Despite what some eBay sellers say the 240mm Tele Xenar isn't listed by Schneider as covering 9x12/5x4, there were two versions of the 240mm f5.5 Tele Arton, the one in a Compur #2 shutter covers 5x4, in a Compur #1 6x9. Also be aware that one listed on eBay is in a shutter for a different FL lens so the aperture scale is incorrect, it's probably a shutter for a 150mm f3.5 Xenar.
Those of us who are long time LF users don't switch lenses between lens boards very often, switching lenses on a 9x12 body is not something you would want to be doing frequently, and not when out and about shooting. I looked at attaching a bayonet mount to some lenses to use on a KW Patent Etui, around 2008, there are people who have done this with Pentax K mounts.
Ian