I think the construction of hte JTV59 might make that difficult. The Vol and Tone knobs are actually recessed below the surface of the guitar as the curved top of the guitar goes from the edge towards the centre. This will pose a problem when you try to install the knob pointers beneath the knobs. I think you will need to either raise the knobs to provide sufficient room for the pointers to rotate properly beneath them, or do some surface reconstruction on the guitar top. Personally, I wouldn't do either of these things.

The idea is a good one - in fact I did exactly that with a Les Paul that I own. I just don't think the installation is practical or worth the trouble on the JTV59. What I do is simply use the visible numbers to guide me. For instance, with the VOL knob at max (10) I know that from my normal playing position I can just see the number 8 on the dial - the number 7 has disappeared from view. That tells me that at any point on the dial the actual setting will be 2 numbers higher than the lowest number I can see. In other words, if I want a setting of 7 I wouild rotate the dial so that I can just see the 5. Works for me, and keeps the guitar intact.