So for this setup I’m going to recommend Star Log Deluxe Uplifted Animals you’ll want medium amphibious creatures with the natural defense armor bonus.
Leonardo has a sword and is probably a combination of Soldier and Envoy. Blitz fighting style and Melee striker seem like the obvious chances.
Raphael has Sais and a temper, I want to say Operative with the Sai being a one handed operative weapon with special properties.
Donatello has the bo and does machines, including time machines. So Mechanic?
Michelangelo the nunchaku.
I need to revisit my TMNT lore before finishing this write up.
Krang could be a contemplative in a Power Armor as many have suggested.