The question becomes:
How effective in the four prime footman roles (Infantry, MP, Commando, and scout/recon) will BD be, vs the same money spent upon unassisted infantry. Mind you, each of those roles has sub-roles, and various overlaps. But, Either they are anti-military forces (Infantry), Civilian and Base security (MP), sneek and Peek (Scout/Recon), or sneak and kill (commando).
That an F-15E Strike Eagle or AGS outfitted FA-18 or F-14 can wipe out an entire company in one pass under the right situation is unimportant... No infantry is expected to survive dedicated air-ground assault. Any that do are a bonus.
Thus the question is, is a BD trooper more likely to survive and/or accomplish the mission than an unarmored man.
Oh, and Aircraft can't do most of the MP stuff.