what can and cant we change on droid and be able to update with oem roms

Just wondering wwith all our mods going on on the droid what can and cant we change and still be able to update if we want to use a official rom and not fail its check? this way i can keep track and back ups of files etc in case i ever need them.....

 

I don't think there is an answer to this question. Something that doesn't get checked now could be a big deal later. I'd keep backups from every so often so you always have the choice of reverting. They arfen't that big and nandroid makes it no hassle.