I do not plan to have Local Coop atm as it may be difficult to implement with how the Sand Box Levels and Giant Boss Camera operates!
However, it should be noted that if you have two systems, its very easy to set up a LAN session for KoH and coop. If you host a room on one system and on the other join a game session without putting in an IP Address, it performs a local host which allows players to play the game in the same room!
also yeah, it is a big point of having to redo the levels over again and learn from experiance to beat it. That doesn't happen too much in games these days!
Also, in regards to Demo Jank, I have a big update planned for tonight which should address some of that!
Thank you again for the kind words!