It seems a weird idea, fitting a poorer trem on a guitar that wasn't designed for it just for the looks. There are some mods worth making on a low-cost guitar, but this certainly isn't one of them.

Sounds like they want something akin to this: https://shop.fender.com/en-GB/electr...176730718.html

You'd certainly want to fill in the existing trem cavities, and then rout out a new trem cavity on the top. You'd need to strip back the finish and redo it completely. It would be far easier to get a new hardtail body blank and modify that. Cheaper too. As it is, the mod will be far more expensive than the guitar. It would be far cheaper to buy a Squier Jag or Jazzmaster!