You could drill and tap some holes (maybe something like 2-56s) in the frame lock side to hold the scale on. You may need to cut a relief slot in the new scale to give the lock bar clearance when disengaging it. This maybe dependent on the lock detent and washer thickness on the lock side.
The other minor problem would be if the edge of the frame lock side is beveled, it would leave a gap. Another minor item would be that the lock side will be thicker than the other side, unless you added scales to both sides.
Another approach would be make the over scales larger than the handles and inset them like Spyderco does with some of their FRN handles. May take some tinkering with to get the fit right and also make the lock easily accessible and workable. It will bulk up the handle. I used this approach on a Kershaw Half Ton. I had to tinker with the scale shape and contour so I could easily work the liner lock. I used wood so I also had to design it to avoid having places where the end grain may chip or break around the perimeter of the liners.
You could make a mock scale from wood of other material, then attach with 2 sided tape just to get an idea how it would look and feel in your hand before you start drilling and tapping holes.
Do you have a frame lock that you are thinking of modifying?
Ric