We can't expire keys, and we can't compress ( =randomize) scripts. The one thing that we do is discourage key re-use. We should not abandon the one good practice that we are capable of doing without a damn good reason, even though we are pretty confident that we are safe doing so.
Thanks for your insight, very interesting. The way I see it now is, if the person holding the single-address account doesn't care that much about his money being stolen (like maybe he only keeps small amounts there), then this approach would be sane. I mean, I'm mostly concerned about this patch having a negative impact on some other unrelated bitcoin user, or the network as a whole. For example, could this behavior make another user less anonymous, or make some other client break (because there is a direct cycle - an input is the same as an output), etc...