To clarify I don't mean delete the transport ships, but instead give them more uses. The land combat has had some changes over the various versions but I find it still quite boring. So why not make your land forces compliment your space forces?
- Perhaps give dead planets a bigger role by making it possible to make temporal bases with an army stationed there. Perhaps giant ground to space canons, supply bases for foreign campaigns, ftl inhibitors on multiple planets. Hidden production sites for smaller ships like corvettes/destroyers, hidden bases for fighters and bombers to protect a system. Secret research labs that give a tiny bonus to specific fields of research like: computing, voidcraft, biology.
- Boarding pods fired from your troop/support ships which can take over enemy ships.
- I don't know if the calculation in the background is the same as the visible representation but if battles are resolved in lines like some other paradox games, why not add artillery or special units?
- Maybe the experience level of your units/ships could be more dynamic. For example if you have a lot of army academies/fleet academies could give you a higher experience base level. If you have regular exercises the, fight in wars regularly experience could increase. On the other hand the experience level could slowly drop to the base level after long times of peace simulating people retiring from your forces.