I've just stumbled on a sql server book that said it is possible to globally "SET ROWCOUNT OFF" either for the target server or the user session. This is achieved by disabling the DONE_IN_PROC message. See:
http://books.google.co.uk/books?id=fw9G ... &ct=result
I maybe wrong but it seems this would solve the issue with triggers but still allow the the toomanyrows excpetion to occur when under circumstances other than a trigger firing.
I have not tested this at all, but I thought it might help...
Christian