I think it is a bad idea to create a new call opcode.
For a long while I was meant to create an EIP to clarify the range of precompiles, but finally did it: https://github.com/ethereum/EIPs/pull/1352 (Also added a topic here: EIP-1352: Specify restricted address range for precompiles/system contracts)
I think with having an accepted range specified, this cost reduction EIP would be much simpler to be specified. I would actually propose to only reduce the cost for STATICCALL since precompiles should be called with that, given they do not modify the state.