Hummm, heres my thoughts on the matter.
Ivy B> = Razor Leaf/ Leaf Blade. Unlike his other attacks this is a close range one where he spins his leaves like a chopper. Like Link's up B he can recover with this move (EVER character has a recover move. . .remember "you must recover!". Ever Zero suit has a recovery move with is a Bv teleport)
Squirt B = bubble beam/ bubble or water gun. This one is tricky. . . it could be anyone of the 3. I cam personally see Bubble beam being a bubble rip of Char's flamethrower so I would like to hear some ways it could work. And depining on how Water Fall works I can see water gun being like FLUDD, making Squirt he edge garder of the 3 (Water fall seems like it can cause a wall like version of the FLUDD and can keep going even after Squirt is off. )
Char B^ =. . . Im going to go against the grain and say Flare Blitz, Outrage, GAGI IMPACT, Earthquake, Heatwave, Dragon rage, Dragon rush or something powerful/ brute and power house like. Seimic toss to me sounds too much like like people pushing their love of Anime Char into this (he doesn't even learn that attack in the latest games and Bowser already does a attack somewhat like it. . .abit moot cause Pika never learned Skullbash and Zero has the whip but still) and Fly to me sounds too gentil. . . if he is the big daddy power house of these reptile-like pokemon than I would hope his attacks are all mostly brutal.
But when I think about it they can all work to truely be one big character.
Ivy could be anti-air (B and B^ to counter air and rank up damage), Squirt could be anti-edge (B and B^ to edge gard but no damage) and Char could be the finisher with kill moves ( B> and maybe B^ to send enemies flying).
Meaning, you could use Squirt to play the run game, dodging attacks and doing mobil attacks like his B>. Than change to Ivy to rank up damage with ranged attacks, messing up their air game. If he gets toss around his Up B and B> can save him. Than once you got their damage up some use Char to send them off the stage with attacks like his B> (and Im hoping his Up B). If they try to get back than edge guard with Squirt's water attacks.
That actually makes sense to me. . .they all have to have something their focused on. Squirt-Speed and edge guarding/ Ivy- Damage racking and recovery/ Char- Killing attacks and recovery. Adds up to me.