Will it be possible to fit base and Daimyo content in the main box?
I don't work for them and don't know if they will answer questions on BGG or not. But! They said this in the comments:
yes, we are designing the insert to hold all of the KS components and expansions
However, the question of "all base and daimyo in the main box" seems dimensionally impossible given all the other inserts we've seen so far. Putting it all in one (regular) box seems to only work with bags or if you do the double box hack.