This thread that Mets linked to is awesome. There's some great smart-ass commentary and some people actually played a test game to see how it would work out. At some point, these identical suggestions should probably get merged together (and I'm sure there are more like them out there). There is some good stuff in these old threads.
Also, in the two threads linked to, I can't really find any reason for this being rejected. So maybe we should keep this one in the active suggestions forum and try to pull these threads together (especially given what the OP here looks like).
Go for it. I'm normally opposed to minor variants on existing gameplay, if the only real reason for doing it is just so that players have more options, but I think that no reinforcements is a different enough style of gameplay to warrant serious consideration.