I get what you're trying to accomplish.. but I suspect that by the time you properly engineer the setup, add the rigging to make it work (not only runners but extra sheets and blocks, winches?) you'll be money and convenience ahead simply by going to all hanked sails. I absolutely agree that a luff tape sail is a PITA when single/short handed.
So if there's no furler in your future modifying your luff tape sails to hanks makes the most sense to me. One other angle is that you'd be creating a bit of an oddball Niagara 31 - maybe good maybe not so good when it comes to resale.
Also what you're contemplating would really be a double headed sloop, a true cutter rig would have the mast further aft in the boat and/or utilize a bowsprit to get the proper geometry of a 'cutter' rig. I suspect the 'double slot' effect would be noticeably better only in mid range reaching conditions and only when properly trimmed.
Adding a temporary wire stay for the smaller sails as a so-called solent stay might work - it could go to the masthead or very nearly, and attach as close to the forestay tack as possible - a stronger part of the boat - negating the need for runners but precluding using two sails at the same time.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)