This would be handy for DJs.
Problem
There a quite a few 4/4 tracks out there with an occasional bar with 2 beats in.
Symptom
This means that by the end of the track the first beat of the bar is falling on the 3rd warp marker in every bar (ie the ones ending .3).
When you come to mix in the next track, or apply any effects , these are now out of time.
Solution
You can just adjust the quantisation, but this isn't always ideal.
My suggestion is a button to redefine the first beat in a bar. When toggled, this would make the next beat to occur the first beat of the bar, with the 2nd, 3rd and 4th following.