Warp stabilizer does not work for all types of footage, especially when something in the shot changes shape (time lapse of setting sun in windy conditions for example).

By simply choosing an area to analyze, this problem can be circumvented. This can already manually be done in After Effects, but it seems only logical to be able to analyze a selection within premiere, and this could probably also speed up the process as less pixels have to be analyzed.

This would probably mean that "subspace warp" is not possible, but in these situations this is often not wanted anyway.