I proposed the same in BIP114. I wish Satoshi had designed that way.
But I’m not sure if that would do more harm than good. For example, people might lose money by copying an existing script template. But they might also lose money in the same way as CHECKMULTISIG is disabled. So I’m not sure.Another related thing I’d like to bikeshed is to pop the stack after OP_CLTV and OP_CSV. The same pros and cons apply.