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.