But Lordy, the argument that he couldn't/shouldn't do something like that because (horrors) it would raise ethical questions about what Slayers do, or because it would make poor Angel (and now poor Spike) look bad makes me want to bite tent stakes in half.

Agreed, which is why I specifically pointed out that that was not the argument I was making. :-) Complicated is good, moral grey zones are good, just as long as people are aware of them and don't just look for one side to be 100% right and the other to be 100% wrong.