I agree on the realism. However, the problem now is that each variant now occupies a slot in in the mission that cannot be replaced with another type.
Thus instead of 8 gazelles available for use however the pilots choose to fly, we wind up with a 2/3/3 or 2/2/4 split or similar, which for a pilot who wants to fly one of the more in-demand variants, forces them to leave the server and fly somewhere else.
It certainly would be possible to have these configuration details be a function of loadout, MiG-21 already does that if you arm the nuke.
In that way, gazelle fans can actually hang out together without being forced to fly a specific variant.
--gos