For gunboats:
Remove gunboat turret dispersion and turret splitting for normal turrets, split for dedicated anti-cap turrets
Merge the role of bombers with gunboats by removing bombers and giving gunboats neutralizers, scorchers, and nova torps.
Make Cruisers and larger immune to snub CDs (by restricting snubs to low radius CDs). Gunboats and larger able to CD other caps with a dedicated high-AOE CD - but remove solaris loadouts from caps.
Downgrade all gunboat shields to the current medium to make it squishy enough to for snubs but give gunboats 400 cruise to serve as interceptors.
TLDR: Gunboats serve as the interface between snubs and caps. Caps without solaris have had their ability to counter snubs nerfed, and snubs can no longer force caps into confrontations without a dedicated gunboat - and caps rely on gunboats with their current level of area denial against snubs (IE, they can only shoo them away, but snubs can indefinitely shieldrun swarm anyway).
Mixed fleet engagements would go somewhere along the lines of - Large caps will attempt to fight other large caps as well as kill gunboats - snubs will attempt to fight other snubs as well as killing gunboats.
For Cruisers:
Give them higher thrust speed and a 360 CD to be able to actually chase gunboats for longer (while still being slower), and to be able to more easily outrun battlecruisers - otherwise, change nothing except removing solaris turrets to make Mep happy.
For Battlecruisers:
A faster cruiser would make cruiser v bc a bit more balanced.
Remove their traditional CD, but give them a 5k radius generalized CD that disrupts everything in range.
For Battleships:
Decrease the size of all heavy battleships across the board for QOL.
Give them built in, and reworked docking modules to make them useful for gunship and snub repair/resupply (including ammo) so that they provide a strategic advantage to whichever team has them fielded.