Would it be possible to mod the stabs on a Filco from Costar to Cherry?
Possible, but a tonne of modding would be required. Really not worth the effort.
So it's not as simple as desolder switch, replace stab, resolder switch?
No, the stab holes are a different size. And the Costar stab wire won't work with Cherry stabilizers. I can't remember if the Cherry wire works with Costar but I don't think so. Also plate mounted Cherry stabilizer housings aren't the same design as PCB mounted so there's that to take into consideration. Stabilizers aren't like switches in the respect you're referring to.
Correct here. Costar and cherry wires are not interchangeable. They are completely different shapes and there is enough of a size difference in the diameter of the wire that it wouldn't work on that front either.
There is a style of stab hole that will work with both plate mounted Cherry, and Costar. Though you will not find it on a stock plate. Those will only support the type of stabilizer that they were designed for. It would however be possible to mod a cherry plate mount hole to fit costar but would require a lot of VERY careful work with a file. Both cherry plate mount and costar stabilizer holes can be modified to make PCB mount cherry stabs work but will require a different PCB unless you are building a frankenboard.
Also, there are no pcb mount costar. All costar stabilizers are plate mount and Alps switches are their own stabilizers of which there a a number of slight variations all being plate mount as well to my knowledge.
