Rather than re-enable OP_LEFT, a NOP could be re-purposed in a soft fork.
OP_DUP OP_HASH160 [pubKeyHash[:LEN_PARAM]] [LEN_PARAM] OP_LEFTEQUALVERIFY OP_DROP OP_CHECKSIG
A B L OP_LEFTEQUALVERIFY checks if the leftmost L bytes of A and B match. If not, then the script immediately fails. If either array is less than L bytes or if there are fewer than 3 values on the stack, then it also fails.
The OP_DROP is needed as the new opcode must count as a NOP for legacy nodes.
A change like this would only cause a once-off improvement in efficiency, so it is less likely to be worth the effort.
It also requires most clients to be updated to support the new address system.
A different BIP could be added for that.
An alternative way to add new opcodes is to use a different script engine like with P2SH.