Joth, I would think not twice but three times about making mods to a John Dunlavy design. His crossovers were very complex and tailored to the specific drivers he chose, and even the wire he utilized to connect the crossover to the drivers. Such simple things as changing the mounting hardware and soldering connections might be experimented with only because they are easily reversible if you muck up something. You can also experiment with spikes VS absorbent footers. Your flooring composition and room characteristics may determine which works best.
John Marks has written in Stereophile about an engineer in the Boston area who modified a pair of Sovereigns. Unless you have an engineering background I recommend leaving well enough alone for any electrical changes.
The grill cloth was stretched over a square metal tube framing which was designed for a friction fit around the front baffle board. Without that it may be very difficult to create new grill covers.
Tbg if you owned Sovereigns maybe I can't question their initial pricing but when I bought Duntech Princesses (the next model down from the Sovereigns) in 1990 they were about $8,900 and the Sovereigns, being a much larger speaker (360 lbs. VS 180 lbs.) were near $20k and soon after they went over that.
I know that guy in Tennessee that Tbg referred to. He got his before 1990 and still has them, for whatever that's worth.