For now, know that generating RP will require actively furthering faction goals - taking and holding territory, etc. Some objectives also bear other battlefield significance than just RP.
Ah but have you heard of the hawk talon a jump pack which you can carry devastators with their weapons
they them to be very rare and only one chapter is using it if i got the text right ^^ so would be nothing good for EC
What about Psyker powers? I know they were said to be part of a loadout, but if your char is a psyker, it wouldn't make sense to make them a null after they switch shiney suits of powerarmor, right?
They arn't a null, just not psychic. This is one of those things that has to be glossed over, since your psyker jsut got blown into particles by a battlecannon.... Alternately, imagine that his reserve of psychic power has run dry for the time being so he resorts to other methods.
If you are keeping a persistent character, dying won't make a sorcerer any less of a sorcerer than dying as a devestator would make you a scout. Also, if psychic powers are depleted for a moment, it doesn't stop making them a sorcerer like "oh, you're done now. No more sorcery for you." It doesn't HAVE to be glossed over, as many players are looking forward to being sorcerers and playing those with psychic potential.
Likely, they will always have access to some default power, like in the tabletop, you can always take the default power from the set, but better/different powers will take RP, just like upgrading your bolt pistol to a plasma pistol.