Floatplanes, if modeled, could be useful.
They could be available in ports, currently are none. I've long argued that there is no reason to exclude Vals, Kates, and SBDs from ports--short takeoff and get the hanger queens flying. MG/small (100-250 lb) ordinance-armed floatplanes could ward off a landing party, no?
They could also be used as AI-controlled objects scouting for enemy carriers. That is, if you have a CV group in the area and an AI controlled floatplane identifies you by being within x range, the "surprise" attack by Milkman CV groups is out, or if on the ocean blue and in attack range of an enemy CV group, the enemy CV group in the area is alerted to your presence. Thus, you send CAP out to cover your convoys/CVs or take your chances.
If they were used like a port launched C-47, only some would have the proper payload and I don't know if any Seaplanes were used to drop paratroops--doubtful but since I don't know I'll leave it to you folks to figure out.
But some could carry substantial payloads and would be useful for resupply.
Also, if resupply convoys and merchant shipping become important, they'd be valuable for spotting those (again AI), or attacking as a bomber (H8K, PBY, Short Sunderland, some of the Italian jobs I think the Cant Z506 Heron carried a Whitehead Fiume or maybe as much as 2k in ordinance). They could grant perk points for succesful convoy escort as well (lose no ships = x points, etc.).
And, they make a nice addition if Submarines ever entered as an AI-controlled object for sub patrol or attacking.
If they are used in a recon role by a player, they should get an increased visibility range so as to make them useful enough to up. That is, a recon flying PBY/Sunderland/Emily would be able to identify an enemy CV group at a greater distance, making them a worthy ride. Since you had spotters with naval binoculars in those planes, this is not historically inaccurate as a fighter pilot watching his butt and dipping his wings to see with his 20/20 vision won't have the visibility a spotter would have had. You could get bomber perk points for doing so (call in a CV from a floatplane, rewarded x points). This makes them useful.
No reason we couldn't rescue downed pilots so that they got a better score for their ride (they were, after all, returned to base) and you got perk points for collecting their butts. The downed pilot could act as a gunner as well.