I did too which was why I went that route, I figured I could always crop a 17mm image (or use the 1.4) to get a 24mm image but not the other way around! And the truth is the 17mm images photos got me to the point that my clients rarely want anything wider than 24 now, crazy way if looking at it but true....
The biggest drawback with using the TS-E 17 on EF cameras is the filter issue, this is negated by using it on the R cameras and using the filter adapters. But the 'solutions' for the front mount filters on the 17 are not really very practical or cost effective.
But the functionality the TS-E's achieve working with the TC's really is superb, I have the TS-E 17 and the TS-E 50 and both 1.4 and 2x TC's. This small kit gives me T/S functionality at 17mm, 24mm, 34mm, 50mm, 70mm, and 100mm, basically it covers everything....
The TS-E 50 is an unbelievably accomplished lens that is superb for exteriors, product photography, architectural details, 'macro' etc etc.
I know what you mean about photos vs images! I am a transplanted Brit, originally from Sussex, who works mostly in Florida, my clients only talk in terms of images so I have awkwardly adopted the vernacular.