I've read at the Big Book of Amiga Hardware that a lot of CPU socket accelerators for the 500/1000/2000 tend to be electronically compatible. The same probably holds for the CDTV, but you probably won't be able to seal up the case afterwards, provided you can mount the accelerator in the first place. Overheating might be another issue.
For a minor boost, you could drop in a faster 68000 (14 or 20MHz) or an 010. I'm almost certain that would work.
