[tunabreath]

I'm fairly certain that the primary reason airsoft BBs are spherical is because it's
a) the most inexpensive shape to produce with acceptable finish tolerances
b) easier to design a working feed mechanism and higher capacity magazines for any kind of automatic or otherwise self loading gun (because a sphere can be fed and fired in any direction)

It has little if anything to do with actual performance, and neither of those factors are a priority when looking at high precision setups like target shooting and sniper platforms.
If cost were a major issue, I imagine fewer snipers would be buying Maruzen SGMs. Likewise, feeding is not as much of an issue for much simpler manually operated designs.

Look at air rifles. Plinkers, blowbacks, and self loaders tend to fire .177 BBs because they're much easier to load/feed. Most target rifles fire .177 pellets instead, because they're more stable in flight.

That said, fin stabilized projectiles for airsoft are a terrible, terrible idea. Look at those RAP4 ones. They simply suck. It's because maintaining tight tolerances on such a complex shape is extremely difficult on such a small scale over such large quantities.

Far better would be the common 'bullet' shape. There's a reason real rifles fire them. Or even conical/minie ball style projectiles, like air rifle pellets. The flared end keeps the projectile stable in the same way fins would (as well as providing a smaller contact surface with the barrel to grip the rifling better), only with a much simpler and more easily manufactured shape. It really depends on whether range or stability are greater factors after testing whether a boat-tailed/teardrop shape or a flared/conical shape is better.

The main problem I can see with a PURE football/teardrop is that it's difficult to seat it in the chamber the same way every time. It needs some kind of cylindrical or two point shape to seat, however the ends are shaped.