My TLA-1 required deepening of the cavity to fit a proper blade switch (CRL, Gotoh, Oak Grigsby).
There was plenty of wood to do this but you want to be sure to have enough clearance so none of the solder lugs make contact with cavity if it's shielded.

Also worth noting, that the cavity is too narrow to accommodate full size (24mm) pots, if you're looking to upgrade those as well. Again, there's enough timber there to to do it and still be covered by the control plate.

Further to what Bakersdozen said, when you file the switch lever slot, file it from the front (the shiny chrome side) and only file in the direction away from you. This will minimise the risk of flaking the chrome plating (or nickel whatever).

A small flat jeweller's file with teeth on the sides works great for this. Even one from a cheap set will work. The control plates are typically soft brass that's plated.