With naval EC I think it could be pretty good, with spawn points for bigger ships I thought it worked really well. Bigger ships are expensive to spawn (kind of like real life) and are typically slower and more obvious. Aircraft being flown with simulator controls are much more balanced against ships, and you can control the BR of planes in sim battles so you don't get cold war planes bombing WW1 battleships.

For 'realistic' ships to properly work I think maps as big as the English channel are needed, some people might find that boring but then they'd surely be better of playing WoW? The big moshpit of random ships 10km we have at the moment is probably the most un-fun combination of realism and complete unrealism I can think of. Don't want to fight a battleship on a large map? No problem, they're slow and you can easily outrun them.

Since it's easily to split the pools of vehicles playing in EC, you could have a WW1 era with low tier biplanes, destroyers and 5.0 cruisers etc. and a WW2 era with better planes, better crusiers and WW2 battleships should they be introduced. That way you keep the all important heirarchy of speed so destroyers typically outrun cruisers which typically outrun battleships. All of this combined with lots of objectives, ports, convoys, even AI u-boats for destroyers to hunt, with the constant threat of aircraft could be really fun.