That is why I donot allow for Support specialists as PC's.
I want to run OW, not a collage of strange characters.
I'm going to risk this, even though I shouldn't, and hope that this doesn't turn into an argument, but have you played Deathwatch, and do you disallow specialists there, too? Chaplains, Librarians, and the like are only HQ, so they don't often run with "regular" Space Marines, either. A beatstick HQ Ind Char CAN attach himself to the Tac Squad, but probably won't, and then the IG equivalents are the same ability. Most SM armies don't field "________-in-training" Libbies, Chaps, Apothecaries, or senior Techmarines, just like IG doesn't train fledgling Psykers, Priests, or Commies.
And now I'm done, so yay If I were playing, and my GM said NO Psyker...er SPECIALISTS, I could still certainly come up with several ideas to play, if not my preferred option (special snowflake syndrome-patient), and Hammer's advanced options, such as Commander and MoO are both very nice, so it does work; it just sort of feels like a limited 40K game without them, especially when the others, each as thinking it follows fluff it doesn't, seems to have a decent integration of specialists. maybe have to stick to Rogue Trader, where EVERYONE is a special snowflake.
If I were playing a dedicated Tank campaign, I'd fail; even there I'd try to have a split of them, the tank, and some other transport vehicle, so some people are outside the Leman, but still able to keep up, maybe in a Tauros, with bikes, or Rough Riders, so some infantry is able to guard their steel behemoth, and have something to do, while not all being one of twoish character types. Not saying it's right, or even easily doable, but I'd hate to have a party wedged into a Punisher, just shooting bad guys with a PGC.