One thing I forgot, the 24mm TS-E is compatible with the extender 1.4 (though I can only speak for version 2), that gives a very decent 34mm TS-E.
I am quite interested in that 1.4 extender and would appreciate some more info if you dont mind..when you say decent, would that be at max shift also and would you say its good enough for professional use..?
I actually use it for work were the 24mm focal is too wide, there is a slight loss in contrast / sharpness, but for me, the IQ loss is marginal, considering you get a very useful focal for a TS lens. I did not notice any problem with max shift, but of course what is acceptable is highly subjective.
Do you already have a 24mm TS-E ? If yes, you could probably rent a 1.4x extender to make up your own mind.
Once again for me, the results are surprisingly good, though I always use a stable tripod, a cable release and LiveView focusing to minimise vibration and guarantee perfect focus.