I'd prefer if they focused on sprucing up politics, both within your realm and internationally. More events, more political options, more "scandalous" options. More repercussions for decisions you make. Save adding in hardcore military strategy possibly for CKIII (by then someone will have probably figured out how to effectively merge the two mechanics). And just so you know, I actually am a proponent of adding in more tactical military strategy to CKII. I love role playing my kings as generals, and I feel in general that kings should be out on the battlefield with their men to at least heighten morale if they aren't particularly great marshals. Only if my ruler's martial ability was 0 and I was totally inept militarily would I elect to sit my ruler out of the battle. But I feel like shoehorning into CKII would have a poor result.
This wouldn't be a Crusader Kings game. It would be a Mount and Blade style game with a Crusader Kings influenced strategy map.
Crusader Kings 3 is a grand strategy game first and foremost, and doesn't lose out too much from cutting the battles, as long as the intrigue and characters are well developed.
Mount and Blade is an action-RPG game which could benefit hugely from better macro-scale management of things. I mean, I don't play Mount and Blade anymore because I find it boring that no king ever dies and kingdoms usually retain the same regions. Childbirth, ageing and death are needed along with CK2-like succession mechanics, which would make that game a great experience.