I've been toying around with the character creation system today and one of the things that I've noticed about it is that when it comes to playing members of the Cult Mechanicus your options are actually very limited, in the sense that it's Tech-Priest or nothing.
In fact I believe the only two Talents that are Mechanicus related that can be purchased if you're not a Tech-Priest are Logis Implant and Electro-Graft Use; however the only way listed of getting an Electro Graft is via the Mechanicus Implants trait which you get from being a Tech-Priest
So if you want to play a Skitarrii bodyguard for the parties Tech-Priest, a Martian Adept or a Mechanicus raised Assassin although you can puchase cybernetic upgrades you'll never be able to do purchase anything such as Mechadendrite Use etc. Things which going off the setting based on Black Library fiction are relatively common to come degree.
I've been mulling over the best way to do it and I think it would be looking down a custom Background route that grants the Mechanicus Implants Trait and allows the player to purcahse Tech-Priest only Talents as Elite Advances, but I'm struggling when it comes to how much that should cost. I'm leaning towards 300-400xp as although the Mechanicus Implants are nice by themselves flavour wise the only real benefit to them is the Respirator Unit which offeres a +20% bonus to resist airborne toxins / gas weapons and a framework that additional things can be built onto with the Talents (which as Elite Advances you'd expect to be at least 50-200xp more than the usual cost depending on suitability.
What do people think?