Multiple GUIs in one program? / GUI Switch?

I noticed in @domsigalasjsbach free Modern 80s Drum Kit Halion Instrument that he created a smaller GUI version of the instrument because the original was too big for some peoples screens

Is it not possible to create two GUIs within one Instrument program and give the user a GUI switch instead of having to create two separate Halion instruments?

Of coarse in the future, offering the protocols for user scaleability either by increment or free size could be good to.