Kerbal Space Program

It would be nice if the next SDK release is written in Mono so the same SDK can be used on all platforms.

It would be particularly nice if portions of it were released as a plugin for MonoDevelop and/or Eclipse. (A MonoDevelop plugin would have fewer dependencies, supporting everything you need right out of the box. Your plugin would only need to consist of a few templates, some documentation and possibly interfaces to external tools used to package texture and model files, written in Mono.)

Additionally, there should be a sanity check script that checks for languages used and routines that don't ship with the default Mono libraries for all platforms, and provides users with information on how to work around the issue. (Either shipping a known external module with the plugin, provided that it's license permits it, to change the code, or to add the routine yourself.)