Hello Ilyuhaghost!

1) There's a problem with saving if you're using non-latin alphabet. Answer and workaround from our FAQ:

This problem occurs on Windows users who's username is in non-latin alphabet (e.g. Cyrillic, Hebrew, Arabic) and is related to the one of the module's ability to read the contents of the folder. There is no instant fix as this problem is deep in the module we're using, and have not created, but there is a workaround.
To play Masterplan, the Windows username must be in latin alphabet (i.e. letters A->Z only), so creating a different user account should solve the issue.
We realise this is far from optimal, and are actively contacting the creator of the module to see if the issue can be fixed; or if we can fix it by ourselves.

2) This was a hard one for us. Level-up system was considered at some stage, but was eventually decided against. While it might've fit the game, we felt it would've taken us to a whole different level with design challenges and content balancing. During game development, one of the hardest things is to cut features and prevent the feature creep[en.wikipedia.org] from stopping the game from ever being finished. True to its retro-origins, the basic goal in The Masterplan is to finish it, not reach maximum level.

3) Multiplayer is another tough nut to crack. Couch co-op mode would more than likely be fun as anything, but again, not absolutely essential to the core gameplay, which is the single player campaign. That said, we still have hopes to include multiplayer in one way or another.

4) Statistics and achievements are something we are going to take a look at at the very end of the game development, when other moving parts are in place. I don't think you're alone with the wish for statistics. :)