I hope you're having a lend
There are pilots in both groups who would be willing to vote for “Swap CAO48 for an FRMS and you can fly a jet” if it meant that their pilot group got to fly the jet instead of the other.
Why not quarantine the turboprop operation to fly the current CAO48 and have a statement in there that says you will consider new rules for any pilots flying a Jet (the unicorn clause - as it's unlikely to be seen). That way, you can satisfy management that any new Jet operation (unicorn-link) will be operated to the same rules as any competitor, and you can maintain current rules for turboprop operations for ever.