Those characters do have spammable attacks but dude to be fair so does everyone else in any other fighting game and ya know Drake, Sackboy and other heavy projectile characters are made for keep away which means they have to rely on every one of their tools, if there were limits to how much Radec could use his grenades, machine gun, sniper ect. if you were in a stock match and you happen to use up all of his projectile attacks, then the only attacks he'd have would be neutral square, forward square, and up square and the reason I use Radec as an example is because if they were to do a patch to try to balance the game this way, then Radec would be rendered entirely useless because at least Sackboy has some decent close range attacks compared to Radec.
Well in Super Smash Bros. Brawl, they have a spam limiter. The more you use a move the less damage it does. They could implement a similar method in this game where you get reduced AP after you use a move too much. On the one hand, I don't like this nor did I like it in Brawl because I don't like the idea that the game is telling you what moves to use.
On the other hand, I would not complain or lose any sleep if the spamming in the game was not so present. So I'd be fine if there was something implemented.