I think a good way that this is often dealt with is for the original author to create a written style guide for their particular application, and for each author afterwards to follow that guide. Unfortunatly, since that isn't defined by the original author, you're going to have to be the responsible one to take care of that :-)

It may be hard enough for you to go through someone elses code, and learn enough about their styles and preferences to figure out what they are trying to do with their code. However, as you're suggesting -- if you change styles for code that you add, it's going to become very tough for anyone to read it (possibly including yourself after a few weeks of maintenance), without getting a headache :-)

I love documentation. Perhaps what you can do is create a document, explaining the currently used style. Then, if there is an area where you feel a style could be improved (and it sounds like there's plenty of them), change both the code, and the documented style guide, at the same time. Yes, that can be a big deal, but it's probably going to be much easier to do that, than to maintain two seperate styles :-)

I'm very fond of the Style Guide for P5EE, you could always use something like that as a basis.

Good luck!
-Eric