I wouldn't want to discourage anyone from working on something they are interested in doing, but you should take a close look and get a realistic estimate of what replacing our home-grown C program called "jburg" with a completely different implementation (also called jburg ;) ) would entail.  We took the original iburg program, changed it to generate Java and did a few other random extensions over the years.  There are several thousand lines of input files written in the syntax our version accepts.  If I were trying to excise C programs from the Jikes RVM build, this is the piece I would leave for absolute last.