Syncing - is there a better way?

Like others, I am having trouble keeping iTunes from overriding changes made directly on my iPhone. Specifically, it removes purchased songs from playlists and adds back songs I deleted from the library. The latter is more than a trivial annoyance for me as my music library does not fit on my device. As such, I only have a sizeable subset (~900 out of 1500 songs) on there, one that I continually trim as I add new songs, videos and apps. If I make the mistake of trying to sync with iTunes, in addition to losing my changes, I am typically treated to a galling sync-failed-because-you're-out-of-space-type message. The only way around it seems to be to pre-emptively go into iTunes and manually uncheck each and every song I deleted before plugging in. Needless to say, I gave up and stopped trying about a year ago. Before I completely throw in the towel and buy an Android phone when my contract runs up, is there a workaround?

Problem seems to boil down to one of "syncing philosophy". I want changes made on my phone to overwrite what is on my computer/iTunes - across the board, no ifs, ands or buts - not the other way around. In the new mobile-centric world, one that Apple has in large part driven us to, this is the way it should be. Why is it not even an option?

Thanks