BoE had some neat ideas but execution was bad imo. I was always staunch supporter of realism in cRPG but after trying that mod I'm sure realism is not the way. Will work on cRPG like mod myself when Bannerlord mod tools are released, my ideas of cRPG like mod actually takes Krems and ladderpaulting folks as basis of experience, not the other way around. Think that hardcore players will be satisfied with vanilla Bannerlord multiplayer and won't ask for more, that's why I believe that next cRPG should offer something silly and different.
As for Strategus, that's huge undertaking. Never liked the way it was implemented in Warband but there honestly isn't any other way so it will probably stay the same for Bannerlord. If I could crack it then design would have to be equally silly like my version of cRPG.
In short, grind would be reduced and changed into something else. Variety of items would be extremely important. Names have to be funny, historical facts are out. Objectives have to be different and various and support other ways of playing the game. Would be great if there was a way to support different game modes inside same map so that people can play the way they want it and not bother others. But that's huge call, something I'm sure Bannerlord won't support out of the box and probably won't be possible to implement by scripting.
What I like in BoE were bots. Think that every gamemode could benefit from system where human player is controlling small team of bots.