Cross training is a great idea for semi-autonomous fire fighter merc teams. My skillwires give me some decent backup skills - armorer, first aid, gunnery, heavy weapons for example, if only at rating 3. Thinking about it, I would assume that a lot of the smaller merc outfits would heavily utilize skill wires to make up for skill set gaps.
If we establish the absolutely-must-have-or-we-are-screwed roles, we can all cross train with one or more specs as well as our primary focus.
To my mind the roles that need to be covered in a 6 - 8 man team include these (might have missed some - its late in the UK) - obviously not all to a high rating, but at least a nod towards competence in all or most areas.
Driver
Gunner
Medic
Magic
Face/Hearts & Minds
Mechanic
Demolitions/EOD
Comms/Hacking
Scout/Recon
Leadership/Tactics/Intelligence
Sniper/Long-Gun support
Heavy/Support Weapons
For our purposes, I dont think that either mechanic or medic need necessarily be a primary role - as has been said, Gunner/Mechanic is an intuitive combo. So is Magic/Medic or Magic/Face when you come down to it - with all the really big bang bang and massive armor going on in a merc unit, how many mages are going to be heavily invested in fireballs and stunbolts? The scout/sniper is an obvious combo too. I know that I chose a pretty niche speciality myself, but the skillwires allow my to at least provide some level of backup to most other MOSes, or even substitute for them, if it comes to it - which is why I spent about as much on Active Softs as I did on Augmentations.
And that is without the basic military capability that DY has outylined with regards weapons and physical skills, which everyone will obviously have to some extent. Just throwing this out here - dont mean to sound like I am teaching people to suck eggs.
Laters.