Perhaps a quick & dirty solution might be to offer an option similar to the following:

Talent (A La Carte): You may purchase any talent, from any tree, at any time by paying 1.5x (round up to the nearest 5) the listed XP cost +5 XP per talent previously purchased in this way. Increase the cost to 2x for talents in specs that the character does not have within their career and 2.5x (round up to the nearest 5) for talents in specs that the character does not have outside of their career . Talents purchased in this way may not be used as a prereq for any other talents.

This would (seem to) largely eliminate the "slacker player doesn't want to spend the time gaining XP" objection as well as potential pitfalls that may come with allowing everything without penalty or restriction.

An interesting approach. Not 100% sold on it just yet, but still a pretty solid suggestion.

Librarian - you should really take a look at Brashfink's work. He addresses (or is working to address) a lot of the concerns you're bringing up.

It seems like the two of you could join forces, at the very least...

https://community.fantasyflightgames.com/topic/191773-on-the-edge-rpg-generic-conversion/?hl=brashfink#entry1858603

I'll take a look at this when I have some spare time at a computer. Work is keeping me really busy this week and I don't have the same online time as I did at the old job (at least not yet; training).

Again, this simply bring us right back to the same issue -- if one Talent is more "powerful" than another, then give it a higher XP cost... or do a better job balancing the Talents. Don't create 26 versions of the same Talent or progressions of Talents that stack in effect to the point of causing a wreck.

If the Talents are balanced and of appropriate XP cost, you don't need to lock them behind an extra access cost in XP or an entire tree of prerequisites.

If your second edit is true, and it's a tradeoff , then that's the balancing factor in and of itself . At that point, the extra cost of access becomes simply a game designer trying to discourage one sort of character in favor of another out of a desire to have characters specialized in their "dramatic roles".

(I'll forego bothering with the whole " Mary Sue " thing, which at this point is just an empty term that means nothing more than "character who doesn't suit my tastes".)

The talents are balanced by the progression costs it takes to get to them. There aren't 26 version of the same talent, there are talents that have similar names i.e. the Master (Insert Name here) or Natural (insert name here). But they all do a different thing, usually something thematically appropriate to what tree they are in.

The talents are balanced by the xp costs required to achieve them. There is a reason Field Commander only costs 30 xp to get and Master Pilot takes 75. You differentiate between Access and Progression costs, they aren't different, they are both progression costs, (technically because you are also gaining class skills when you get a new spec).

I also disagree that the designers are trying to get people to focus into their "dramatic roles" as I don't think the system really rewards players who are laser focused into a single area of expertise, in my opinion it makes the game really boring (and more difficult for your GM) when you're rolling 5 yellows, and a green, because you have a 6 in a characteristic and a 5 in the skill. It is boring to win all the time.

As to foregoing the Mary Sue, I don't really care what you call a character that can do all things and do them at an expert level all the time, I'll just reference the previous paragraph, that a character that wins at everything all the time isn't interesting to me. To me, that is what this free-form character generation and progression system will promote. So I guess, yes, a character who succeeds at everything they do, in any situation and never loses is a character I do not care for.

Could that not be addressed by having prerequisites for talents that don't involve talent trees? For instance, Superior Reflect may cost 25 points and require Improved Reflect, which costs 20 points, which in turn requires three levels of Reflect purchased at incrementally increasing 5 point costs 5... 10... 15... 20... 25 = 75. And, that structure means getting to Reflect 5 would require an additional 15... 20 = 35 more. This doesn't require a tree, or picking up unrelated talents you don't want, but Reflect 5 with the Improved and Superior upgrades would still cost you 110 Points. Doing the same with Parry would cost the same, so both would be an outlay of 220 character points. And, you still don't have any of the cool saber maneuvers from the assorted trees that are out there, and would also have associated costs and their own prerequisites. You don't have to have a tree to balance it, or still be playing a variation of this game rather than throwing it - and its awesome dice mechanics - out with the bathwater. Of course, one could just create their own custom tree. Insofar as its thought out, it wouldn't break anything.

Your build is very true to what the core of the systems is, that I concur. I can see this kind of frame work also allowing cool social and roleplay-related "min maxed builds". so I am really cool with it

I am sure that, if this lines continue adding careers, signature abilities and special powers, we will eventually have any combination that we want in specs... or so I wish