I dunno, after you do the rewrite, then what? If the bureaucrats won't ever let you make incremental fixes/cleanup, then even your rewritten version will eventually rot.

I think the idea of building software "the right way, once and for all" is mostly just wishful thinking on our part. Even the ideal rewrite will have ongoing maintenance that needs to be done.

Therefore, my only two options in that situation would be to a) make those incremental changes as part of features without telling them (estimated as one chunk), or b) look for a new job.