Eclipse could be rebuild from base specially designed for 3dgs. I've been looking into it, you could mod the existing C/C++ eclipse but I couldn't get the lecturer to work with custom lite-c keywords, nor did it pick up the path to acknex.h properly. It would also take quite some setup time for each new workspace or other machine as there doesn't seem to be a complete settings export.

You could also compile a new eclipse from the basic framework and create your own lecturer, etc. But that is quite a pile of work. This option might be perfect to integrate your precompiler.