How about at least compiling it for ARM? I'm pretty sure it wouldn't cause any real problems or require code changes. If you could compile Paint.Net for ARM cpu's then the Surface RT and other Windows RT devices could run it via this hack: http://forum.xda-developers.com/showthread.php?t=2092158
I'm sorry if I'm wrong and it is more complicated than I had thought.
It would be very greatly appreciated if you would at least give it a quick try.
Thanks,
Johnny