I have several problems with the current advancement system.

1) I find it very restrictive (as many have pointed out). There is no room for a Guardsman to be an effective leader without spending thousands on Fellowship or for an Adept to be any use in a fight. Obviously this is a little exagerated but you get my point.

2) As a GM, I seem to have very little control as to how good my players are. I'm not complaining that one of my psykers can drop a man with a thought or that my Assassin/Guardsman can pilot a heavily modified Space Marine ThunderHawk Gunship. But sometimes I wonder at how they got to that point in the first place and would like a little more control over the fact that one mission my Scum shoots two guns without hitting a Hulking Space Marine and the next Called Shot's an Interrogator's head from 30m.

3) Overall, I find it rather boring that to a degree all Scum have like personalities as to all Guardsman and all Psykers. Of course they're not all the same but at the core they are all Scum, Guardsmen, Arbiters, and Tech-Priests.

So my question is, and I hope for as much input as possible, is am I too ambitious to basically let free reign on career choices? Where one of my characters was a former Immigrations Agent and another could have been the psychic advisor to the planetary governor? You could bring in a surgeon from Dusk and then a singer from Malfi.

This would require a lot of work on my part as each of my players would have to come to me for career paths. And at the beginning the surgeon would still be very limited in his choices of skills and talents. But as he learns that the Imperium is more than just a piece of glass in a scared child's hand he would gain possibilities. Also, I would be able to control what my characters get so my kill-addicted Assassin can't get Charm and my super-introverted Psyker can't get Master Orator.

Am I too ambitious?

I don't think you're too ambitious but I do think you might be looking at things from the wrong angle and seeing restrictions on the careers that actually do not exist. While I'm not the biggest fan of the Career Paths, they really aren't all that bad once you get used to what they are and how to use them. Let me offer some counter points to the problems you've found.

1) Ya, it is a bit exaggerated ;-) The Adept in my group is a pretty hard little guy who really knows his way around a las gun. Of course he is Schola educated... at times he's been more dangerous then the gunslinger. Either way, the majority of the restrictions have been addressed with the concept of Background Packages and Specific Home World Options. They exist to add and alter the career paths to better match them to a specific character concept.

Need a Guardsmen to be a leader of men? Write up a background package for Noble Guardsmen that swaps their Fel for S and possibly toss in a few leadership skills early on so they can command men out of the gate, give it some drawbacks and slap a point value to it. Bam! Now a Guardsmen can be a great and charismatic leader. If you prefer, they could use the Cleric career to represent a charismatic and learned officer in the guard. Just write up a background package that would give him the tactical knowledge skills and maybe one or two more weapon proficiencies if desired and bam! another type of officer. It's really only as restrictive as your imagination allows it to be.

2) There's nothing saying you can't veto the purchasing of a skill or talent if that's something you worry about. A lot of GM's for DH do that already.

3) That one is just a personal problem. No where in any of the careers dose it state what personality a character must have to be in which career. What makes you think all scums act the same and all pykers have the same personality. Dollars to donuts, the psyker that was in my group was nothing like any psyker that you've ever had (unless you've had a psyker that was effectively an 8 year old girl who was easily distracted by cute fuzzy things and animals with pink bows). Heck, for a completely different take on a tech-priest, there is an amazing story here on the boards detailing what a tech-priest would be like if that tech-priest was Hunter S Thompson. It tosses every preconceived notion about what a tech-priest should be and tosses it out the window in a most brilliant and hilarious manner. Read it, it's brilliant!

At the core of the careers, of course they are all scum, tech-priests, etc. This is because they are all a rough role, a general archetype of a type of person living in the Imperium. But each career is not an specific career, it's a general type of person who tends to fill a general type of role (and those types of people tend to be, well, that type of person). After all, if I were to mention that someone was an artist, you would have a few canned ideas about what that person would be. You may be right in a few of your assumptions and wrong in others, but there would be certain traits that, more often then not, an artist would have else they wouldn't have become an artist. They will most likely be creative and a very visually based individual. They might be flaky or grounded however, flamboyant or reserved, but they would inevitably all be fairly creative and driven with a desire to create else they wouldn't have become an artist (though there's always an exception).

Just as they can differ, so too can characters in the various career paths. An Arbitrator can be a sleaze bag opportunists who cares about nothing outside of their own goals and pleasures. A Cleric could be terribly shy though devout or charismatic but utterly faithless. A guardsmen can be a snipper who's afraid of getting hurt and a scum could be a truly virtuous vagabond looking to right wrongs where ever he goes.

Guardsmen are not necessarily Imperial Guardsmen but, instead, they are the folks who are drawn to a militarized style of fighting and who live their lives fighting in such ways. Adepts are not all scribes and comptrollers in the Administratum, but tend to be any type of individual who is drawn to knowledge of one form or another (and isn't some walking cyborg who worships machines). A little imagination and a half baked character concept will pretty much give you the specific careers you mentioned, a good and true personality for the character, and even curb the players xp spending to what is logical and natural for the character to have based on their experiences and their underlying concept (as long as the player is in any way interested in playing the concept they came up with). Most any career concept you can dream up (mostly) will fit into one of the eight careers presented in the book -some may need some additional ranks added or a background package, but that's what such a mechanic is there for.

Of course, all of this aside, there's nothing from stopping you from doing away with the career system and just having the players come to you with the skills they would like. However, the downside there is the extra work for you which isn't really needed and a loss of easily attainable focus for the players in regards to their characters which can be beneficial especially for people new to the universe. You may wish to check out Dark Reign as a believe their is a write-up on a careerless system that may give you ideas or help you out in that direction (though i don't think they could get Tech-Priests and Psykers to work with it).

Edit: forgot to include a link... sorry.

On an opposite spectrum and not insulting the prior poster, I feel that I'am a purist of sorts. I beleive in "low tech" games, starting from beginning rank and having the Acolytesearn their xp and rank. In some sense it would be grand to accommodate the Acolyte with a multitude of traits and advanced skills that make for epic play. On a smaller scale, I see the player character as having a very small role in a universe that cannot be conquered in x amount of gaming sessions. This is at least what Dark Heresy seems to be trying to get across to players, readers and game masters. Don't get me wrong, what fun would it be if imagination of the game and gm was distorted by "low tech" all the time. Epic fantasy makes for great campaigns. Conquering worlds and having"uber" high Acolytes making history can be fun as well, but I'am not ready for that. I want the simplicity of the game. I.E. earning rank and xp. I agree with Graver when he mentioned that their can be alot of ideas for characters that don't necessarily fit with matching career paths and personalities. Look at most of the adventures so far. Illumination, Purge of the Unclean, Edge of Darkness and CA. They are all pretty much simple and defined. I know I got off the subject a little bit but let me bring it back to original question. What makes a role playing game great in my opinion is the role play of the character, the backrounds of the character and the interpersonal and personal relationships with self and others. NPC personas, creatures and story are great additions that should be centered around a characters story and actions.

You could just offer Elite Advances...

...Idless