Signature electronics can just barely squeak into an Essence body shape - the controls are a little closer than we usually do. If you are getting the Small Standard shape, then you could add the quick tone switches.
You'd also need to decide if you wanted one set of switches for the overall sound, or one for each pickup (4 additional switches).
If you are trying to add this to something that is already built, we'd have to look at the cavity to see what would fit with the existing routing.