Klinktastic:
We could use any career to bolster our ranks, but some more weapon specialists, ogryn, or even a ratling sniper could be useful.
Hmm, you don't have a cogboy on the list. Though their usefulness depends on the campaign style, doesn't it.
I could try weapon specialist or enginseer if you still need any.
Abhumans are a bit too tempting to loonie up now and then.
Klinktastic:
Weapon Specialists can equally be good at both close combat and ranged combat, so they usually make for pretty versatile character types.
Flamer falls under weapon specialist, and while not CC, it's "not being overrun" role. And shushgun, but depending on the armoury selection available, usefulness may vary greatly.