Yes I liked your solution, which I found earlier via web search.  Definitely cleaner than mine.  It doesn't however, handle the truly pathological case of a malformed DOCTYPE decl as in:

<!DOCTYPE TEI PUBLIC "name removed to protect my client">

I guess a url following the name is required in this case.

Perhaps it's a *bad idea*, but I am trying to allow this by ignoring it.  At least the angle brackets match. Sigh.