I'm getting a bit curious to say the least. Allthough with the succes of CKIII's release I'm starting to fear a bit if PDS will keep up their commitment to Imperator. That being said the release of CK3 might also give PDS a lot better idea what to do with Imperator. There's both a lot to learn there with respect to A: where CK3 seems to succeed and imprator fail and B)) which area's CK3 does not focus on and where Imperator can step up their game to find their own place under the sun.
In category A I would say a clear choice in UI, don't make a game where every choice results in 4 or 5 different modifiers doing something but actually make an impact, do something about the modifyer madness alltogether, and most importantly allow us to develop our country in a long term, mid term and short term direction! In CK3 you have the satisfaction making choices that immediately benefit (like forging an alliance, conquoring shit, etc.) that give you great choices in mid term development (lifestyle choices, educating a kid, work towards a kingdom title etc.) and allow you to think off an execute long term plans (reform (pagan) relegion, map paint an empire, and choose a dynastic legacy.
Some of the design choices in Imperator utterly fail in this fundamental aspect of a 'grand strategy game' the only real choices for mid and long term is which direction to paint the map in or work towards an imperial government. The military tradition give absolutely zero choice in what you want your empire to focus on (it's just thrown together modifyers)) and the resarch is only little better, in the end you'll do everything. Why not give us a satisfying way to forge a trading empire with colonies all over the mediteranee, become a diplomatic citystate with a web of alliances in the middle of an empire challenging federation or league or go full on Roman and go berserk on Legions painting the map (bloodred)? The reworks in relgion and pops are a good step up since at least that gives you something to aim for (focus certain cities on certain tasks or Pokemon together an ideal pantheon but we definately aren't there yet. There is just nothing in the game that gives the short and long term satisfaction and difficult choice that even comes close to choosing an ideagroup in EU4 or a dynastic legacy in CK3
In category B I would argue that Imperator should double down on increasing the relation between pops and warfare (see my proposal a couple weeks ago in the senatus populus), make a deeper and more meaningfull trade system and give us much more meaningfull subject interaction and gameplay mechanics. Even the ultimate empire builder Rome did a lot of their 'conquest' in this age not by declaring everything conquored as an immediate integral part of the empire but left most of the local government intact, Nearly every bigger empire or kingdom would make a lot more sense as some sort of EU4 HRE like federation or league ideally with varying levels of commitments, rights and responsibilities between the leader and the members.