Keep vertexes selection active while going to another keyframe (edit mode)

Hello, Let's say I have a character with an hat.

I select the vertexes for this hat, move it a little, then go to the next keyframe. But on that next keyframe, my vertex selection is lost.

It would be a nice workflow thing to keep the selection active, so I could animate my hat very quickly.

I know that you can assign a vertex group (or put the hat on a different layer); but this requires some organisation = more time.
Since I guess that every vertex has an ID, this should be doable; and I don't see any downside at it.

What do you think ?