WIN Corp is a private company. The public can't simply buy shares.
The only way to change the Board and achieve sole ownership is a buyout of WIN's interest (which I believe has a preemption clause applied to it - ie; it can't just be sold that easily, even if WIN was receptive to an offer). But, I reckon the only way is for StGI members to create a pool of funds and start direct negotiations with WIN - as a starting point. Obviously, they'd demand a premium, or simply refuse regardless of the amount offered. But, Gordon is a businessman first and foremost.
Better still, raise about $20m and try to buy out both sides. It will be decades before earning a return on investment though so we'd need a whole lot of people to be prepared to pay the price.
Alternatively, try to find a new suitor with lots of money to burn. Careful though, because we could end up with a single owner that could be worse than the JV.