All semi hollow guitars I've seen have the backplates glued to the body or body "frame" in the case when the hollow is fully removed instead if carved. I'm not a tone-freak, but, would I compromise tone too greatly if I mounted the treble side backplate of a semi-hollow with screws in order to access all the electronics easily instead of glueing it?
The back plate of a semi-hollow guitar is typically glued to the body or frame for structural and tonal reasons. Gluing helps to increase the rigidity of the body and improve sustain by reducing unwanted vibrations. Mounting the back plate with screws could compromise the guitar's tone if the screws are not tightly secured because the back plate may vibrate against the body, leading to unwanted noise and reduced sustain. However, if you ensure the screws are tightly secured, and the back plate fits snugly against the body, then you may not notice any difference in the guitar's tone. Ultimately, the best way to know for sure how it will affect the tone is to try it and note any differences.