#1 is real, especially in urban/house clearing sorts of scenarios it's damn useful to be able to switch firing sides as needed.
#2 I've never seen or heard of in operational use, and personally I believe it's a statistically insignificant possibility for an organic bullpup design like the AUG or F2000. Stuffing a Mini-14 into a Muzzlite bullpup stock changes those variables IMHO.
#3 should be speed and ease of magazine changes. With practice you can get decently quick on an AUG, but the same practice/effort on an M4 will be measurably faster, especially when prone or otherwise low behind cover.
#4 would be the trigger pull problems. It isn't always a problem as the AUG trigger can be very effectively upgraded and other newer designs like the Kel Tec RDB have solved the trigger (and ambi) problems, but are suspect for other reasons.
IMHO, the only issue that can't be solved from improved/innovative bullpup design is the magazine change speed.
But speaking from an institutional level, if I were buying for a military application I'd take the proven solution with well known capabilities and shortcomings over the bleeding edge every time.