My dream solution would be TS 35, TS 50, TS 85 or 90.
I use the entire TS lineup, but would love to have something in between normal and 24mm.
The gap is pretty large right now.
35mm is a great focal length, and obviously very popular. I'd think it might sell well?
I shoot interiors and architecture btw.
I regularly use a 1.4x TC on the TS-E 24 without a second thought. 24 * 1.4 = 33.6.
There's a video out there of how some hotshot photographer made a signature portrait of some expensive Florida hotel with the help of a huge team of assistants. He used a 1.4x on a TS-E 24. I think he even used a 5DII.