"Still have yet to decide on a design for the Spy; since we're not worried about it".
You can add the checker with the same diameter under Pawn and do nothing!
But there is one impotent thing which you must to do.
It is your interest to publish on picture of the chess set the
name of author and producer and get the license and the patent.
You can sale the chess set with great profit on eBay, Amazon or elsewhere.













Update December 31, 2015: Spy piece created
Check (upon Black):
1.Gi2g4 1...f8f6
2.Ne2d4 2...Nd9f8
3.i3i5 3...g7g5
4.e3e4 4...e8e6
5.f3f5 5...
(Image has been scaled down to fit width of forum; to see larger size, open in new tab and, if using a PC, press ctrl+/- to zoom in and out)
2d diagram: click here
Render of Black's (IvanKosintsev's) view: click here
2D diagram of Black's (IvanKosintsev's) view: click here