Arguably, TFCE with default parameters is better than "regular" cluster-based permutation tests and "default" thresholds. Maybe we could allow threshold='tfce' to make it easier for users.
We could use a comparatively low number, and give a warning that it will be slow, and advise users to manually use different settings if they just want to prototype.

Conceptually, this would turn the threshold parameter into a speed gauge - for those who want to make TFCE faster for prototyping.