Not trying to spam the thread, but I've been thinking about this today, and I put together some suggestions for options that could be available and give more of a Great Crusade era technology feel:
breachers
Sv 3+, FF/CC 4+, Volkite chargers 15 cm, disrupt and (small arms)
This encourages breachers to get close and shoot, but if they get caught in an engagement they're a lot less useful because they don't get disrupt. That seems to me to fit with their 28mm stats, where you want them close and shooting but not necessarily in an assault.
Tactical support squad
Sv 3+, FF 3+ CC 5+, Flamers 15cm Ignore cover or (small arms, ignores cover)
OR
Meltas 15cm MW 5+, or (small arms, MW)
Gives you the classic flamers or a massive pile of meltas.
Heavy Support Squad
Sv 3+, FF 3+, CC 5+
Volkite Culverin 2x 35cm AP 5+ Disrupt
OR
Lascannon 2x 45cm AT 5+
OR
Missile launcher 2x 45cm AP 5+/AT 6+
Gives options for massed heavy weapons not available in the 41st millennium, but each has a clearly defined role.
Predator
Predators with bolter or flamer sponsons have FF 3+
Flamestorm cannon 30cm AP 3+ Ignores cover and (small arms, IC) plus Heavy flamer sponsons 15cm ignores cover and (small arms, ignores cover)
OR
Autocannon 45cm AP5+/AT6+ and 2x Heavy Bolter sponsons 30cm AP 5+
OR
Twin Lascannon 45cm AT 4+ plus 2x Lascannon sponsons 45cm AT 5+
Standard predators, with either an AP, AT, or infantry support bent.
Predator infernus
Plasma destroyer 45cm AP4+/AT4+ plus 2x Lascannon sponson 45cm AT5+
OR
Magna-Melta 30CM MW3+ plus 2x Heavy bolter sponson 30cm AP 5+
Special weapon predators. I assume these would need to be priced a bit higher, but pricing is not my strong suit in the slightest.
Hopefully this is a bit more helpful than whining and vague ideas!