Starsector combat has devolved over time from the variety of situations presented in the missions to more-or-less "two fleets smash into each other". That's probably not going to change, though Alex has mentioned he's unhappy with objectives, but it's fun to come up with ideas that could be used in a hypothetical combat rework.
Some ideas I've had:
Deploy enemy ships with your DP. Lots of logistical problems with this, of course, like the ships would have to appear on the map somewhere they can't instantly retreat or whatever.
Limit deployable DP in some circumstances. For example, battles in nebula-shrouded asteroid fields could be very DP-limited.
Abstract the battle size setting. Battle size dramatically affects balance, so IMO it shouldn't be at the whims of the player. Maybe, instead of a slider, have presets like sector size: small for weak computers and normal for everyone else. If players really want bigger battles, make them go to settings.json to enable a configurable "large" option.
Fast movement between fights. People have suggested various ideas along these lines, but I think simply giving a big speed boost when far away from enemies would remove a lot of tedium from combat.
Instant win/lose conditions. For example, maybe if you destroy/capture all of the enemy's "drive inhibitor" objectives your fleet can instantly escape the battle.
Deploy from objectives. For example, if you control a given objective, maybe you could deploy ships from the side of the map.
My ideas suck to varying degrees, I know, but that's how brainstorming goes. The more ideas we post, the more material Alex can mine if he does decide to do something with objectives or combat as a whole.