Hi. Not actually sure as this heavy duty grip looks like it belongs on a hammer or axe. Perhaps it's just the photo. Once we see more of what you have in mind for this saber then more ideas will come.
Are you planning on a grip wrap for the empty hilt ?
I do not know ...
Maybe i will make some strips of grip on the hilt to hide the switch hole.
I took a picture from you to try to illustrate ...
Just a possibility ...
... but i will wait for the community wisdom and your luminous idea