While that's not all too realistic at company level, but done in some armies, I tend to create mixed companies on a regular basis - I mostly play with force sizes of a battalion at maximum so it's pretty unbalanced to do otherwise. When I am playing a brigade-level battle, then, of course, I'd say this is quite unnecessary.
I usually have like 1-2 high-end platoons and maybe an engineer platoon on cheaper APCs in support. But I'd keep it somewhat realistic usually - like, not mixing tracked + wheeled vehicles, or worse, like attaching a para platoon on some BTRs to a BMP company... that sort of thing is not what I'd normally do ;-) - at least not in a PBEM where realistic force mix is usually part of the agreement.
I only do this mixing with the infantry though, I don't think it makes much sense with tanks.
If you're familiar with the
Cold War Mod, there's even a mixed BMP-2 + -3
platoon formation included for the Russian OOB, which consists of 2 BMP-2s (advanced versions - much more heavily armored than early BMPs AND BMP-3s) and one BMP-3(great firepower but not so great potection, as we know it).
This actually makes sense tactically (though not logistically of course
), as the heavily-armed BMP-3s are intended to provide long-range firepower, and Infantry sections also vary, the BMP-3 section having the support weapons while the BMP-2 sections are lightly equipped for close combat.