SBD, D3As, TBMs and such only real defense is maneuverability, adding formations would just give attackers 2 free kills in the process imo.
If you're in one of these and you have to rely on maneuverability for survival, you're as good as dead anyway.
At least with a formation, these planes could have a purpose in the MA.
As it stands now, nobody takes any of these from a CV because a D-hog carries 2k in bombs and 8 rockets. A TBM can take that much, but it's much slower. The others take even less.
With formations, a now a player can trade speed for 3x as much damage as a D-hog. That would actually make them useful.