So in theory it should be possible to create missions for WCA, and then share them with other WCA players? Maybe gog should have a way to submit user generated levels?

I like the idea..

what file should we upload, and where? :)

Haven't figured out what the save file is yet. As for uploading, that's why I was suggesting GOG should offer some server space for things like this for games that allow level editing!

http://www.gog.com/wishlist/site/offer_hosting_for_player_created_levels