iTunes Match + manually managed music? My iPhone is set to manually manage my music, and I'd prefer to keep it that way. However, I also like some of the features that iTunes Match offers. Is there any way that I can enable Match on my phone, download what I need, and then disable it again without it deleting my existing, manually-copied music?

(The reason I don't want to switch to iTunes Match full-on is a) I have a lot of unique masterings and recordings that iTunes Match will match generically, b) I listen to a lot of one-off tracks that I don't want stored permanently, and c) it feels wrong that I can't copy music from my computer if I so wish, even if my phone is plugged into it.)
Note that iTunes Match is fairly precise in how it matches songs.  A unique recording will probably be uploaded, not matched -- certainly, if the unique recording has a different length than the standard ones, it won't be matched.  If you are willing to potentially lose $25, get iTunes Match and see what is matched.  If stuff that you want to be uploaded is matched instead, don't use iTunes Match.