More "tactical bigships" would be great, once they repair the balance between the energy weapon types. I'd love to have one that is Federation-themed, especially. The Typhoon? The Jupiter? The Scimitar would probably another excellent "tactical carrier", and it does seem to have a battle cloak in the NPC versions.
I'd be interested in seeing some classic ships get extreme makeovers like the Galaxy-X did.
If the Galaxy can go from Cruiser to Dreadnaight with a nacelle and phaser lance added, maybe there are beefy Defiant-X's that are Destroyers?
Maybe a Galaxy-X take on a Nebula that's a beefy sci-ship with a lance?
More X-wing upgrades of classic Klingon ships?
I'd be interested to see extreme retrofits of all the canon ships for awhile. Not all new costumes/profiles like the Majestic but actually mechanically new ships with kitbashed elements that make them mechanically a different class like the Mobius and the Galaxy-X.
Maybe, for example, an MVAM sci-ship with a sensor pod?
Not just kitbashes but outright stated kitbashes. "This is what we did to old Defiants. This is what we did to old Prometheuses."
Maybe call them "Retool." As in "Advanced Research Retool" might be a sci Prometheus. "Tactical Destroyer Retool" might be a Defiant with reinforcements added. Maybe have an escort that's a Galaxy saucer with warp features (and Defiant style nacelles) added on, made from surplus saucers. "Exploration Escort Retool."
STO can't really simulate the "big guns" that a classic dreadnought of naval history would have. DHCs while powerful, don't really work. You'd need ship-specific DHCs with a firing arc of 180 for it to be an accurate depiction. The Jem'Hadar Dreadnought is really just a carrier with one more weapon, like the Kar'Fi.
It seems to me that everyone who demands a true dreadnought or battleship just wants a cruiser with weapons like DHCs with a bigger arc and higher level boff slots than is standard for nearly every ship. It's not necessary for the game. It'd also be too unbalancing. It'd be the only ship people would want to command because it could do damage like an escort and tank like a cruiser.