I don't think you can line a foot spa that has jets.
The only two that I know of that use liners are the Footsie and Belava. They don't have jets but they do keep the water warm and they 'agitate' (can't think of the correct term) the water w/o jets. HTH! :)
Personally, I wouldn't charge for removal if the client had the SL done by you and is having it done, again. I would only charge for removal if it's a stand alone service.
I can't wait to try the Shellac Luxe. It looks fab.