Pay rates and work rules already exist. If they want to give you the 175s, you should ask for nothing less than Envoy book!
Please don't get all defensive about it. I'm not trying to offend. But let's face it, IF they are coming to you for a place to put these 175s, then that's only happening because Envoy voted no and said they would only fly them under their current concessionary contract and nothing less.