If the migration problem is not fixed, all strong players will move on one side and fight the weak. This needs to be fixed before merge
The migration problem will somewhat fix itself on those servers once enough people are 40 or close to it because theres hardly any reason to be in the winning kingdom in a pve only server after you maxed your castle level with a decent garrison.
I added it up and all the researches takes over 2 years to complete so forget staying on a pve server at 40 because of the research and what the hell are you even researching for at this point, even if they added more pve content it wouldn't be lvl 40 exclusive so you are just going to breeze through it with lvl 13 units.
Hero levels maybe? - well I have 5 heroes at 40 and and 3 at 35 and I'm already running out of reasons why I'm currently leveling the 4th hero to 35.
I think a fair share of people on my server would literally rather quit the game than continue to play on a pve only server~
Plus 1 city king is a thing and its pretty nice because you can get a goldcap of 135~ at lvl 40 in a small city with army cap tile and duke which is enough to support 5 stacks of 27 units each which you can have once you finish level 12 30/30 research.