Actually, one of the things they can do to limit fleets and big fleet power is to introduce something in the environment that forces upkeep. Maybe interstellar weather or part wear. I think one of the reasons people can build Titan fleets so big is because, unlike IRL, it doesn't take any money to pay and feed the crew, or paint the hull, or overhaul the engine at 100,000 miles.
A lot of people get caught up in the cost of an American aircraft carrier (there's that line about how its construction money would feed some developing country for a year. Lost in that discussion is how much they cost to maintain. That's really where the drain on resources is. We don't have that in EVE. You can collect ships like baseball cards and they're always ready to go in prime condition. You can fly them as long and as far as you like, but that capacitor will always recharge and shine like new.
I think the PF is that our vast capsuleer wealth pays for the routine stuff, but when you think about it, lots of ships (or even smaller numbers of big ships) should probably outstrip our ability to passively pay for gas. That might be a way for CCP to control large fleet production, and probably make null a helluvalot more interesting place. Force people to pay to keep their ships in good condition, especially when flying. While that probably will amount to a pittance for your common frig pilot flying into FW or running missions in highsec, the upkeep on Titans must be astronomical. Then, you won't be able to afford 100 titans; you'll only be able to afford what you can afford to keep running.
I don't think CCP even wants to make the game harder for the nullcorps, but man would that make it more interesting (imagine having to guess not just the size of a corp's fleet, but its actual condition, and how a temporary drop in money can mean a big fleet can suddenly find themselves having to mothball ships until they can get their economy working again). At the very least, it would explain why nullsec power blocs wouldn't be able to destabilize the empires, Imperial upkeep programs due to their relatively high tax rates would be huge. Hell, it might also make a titan what it was supposed to be again, a kind of monolith that shows up like a hot-dropping space station rather than a relatively disposable ship. It might also spur nullsec corps to action, since the only way to build more ships would be to own more territory.
Just a random suggestion. Thoughts?