I also shoot architecture for architectural clients. For correct perspective, without bending pixels, a TS-E lens is necessary. Yes, the 24MM TS-E II isn't perfect, but it is the best choice right now, unless you want to go for the $5,000 Schneider 28MM which has a larger image circle - but narrower perspective. The 17MM TS-E is a fantastic lens, but I think you would find limited use for it. When I photograph interiors my go-to lens is the 24MM TS, I find I use the 17MM only for really tight spaces like bathrooms and narrow galley kitchens.
Yes, there is the 16-35 F4 zoom, a good choice at a much lower price, but you are still limited compared to a TS-E as you cannot emulate a tilt with Photoshop to increase your depth of field. If you are shooting a static scene, you could stack focus, but that is time consuming and often not successful. You might think that shooting with a 24MM TS-E II at F8, there would be no need for tilt, but I can tell you shooting larger spaces, like a hotel lobby, it is necessary.
I've attached two images of the same apartment, one shot with the 17, the other with the 24. The third shot is a residential lounge. This is where the tilt is really of great benefit. (These look a little softer here, they are tack sharp).