Alright, I've dug deeper into the source code. I still can't even compile it without getting warnings, but atleast the resulting file seems to work fine, so I guess those warnings aren't all that important.
Here's what I've concluded so far:
* Highscoresaver (which was my original goal) will most probably be implemented.
* A level-code system should also be no big problem. I've worked out a good way to display the level code. The main thing is where it will be input, probably I will add a little dialog right at the beginning, even before the 'Xrick' intro pictures (will be easier this way).
* Controls will NOT be reconfigured, sorry. I've looked into it a bit, and it seems kind of hard to do this in a good way.
And finally, no promises made, this might all turn into nothing for all I know, but I'll make an attempt atleast.