I hate to see you lose precious water - if you don't have a constant source of irrigation, think long about draining and starting over. If it means you might be dry for a few years, that, to me, would not be worth the benefit of a clean slate.
Consider the option of keeping GSF and supplementally stocking HBG per Cody. You keep the water, and will slowly alter your panfish population thru genetics. HBG have gained a lot of respect on the forum the last couple years as a couple guys who really understand how to manage them have demonstrated their merits. I admit my ignorance has abated through their research efforts.
If water is that rare, my advice would be to try and manage your existing fishery [GSF] and still achieve your goals. With resources like PB at your disposal, I am pretty confident we'll get there together.
So, determine your ideal fishery [what species do you want] - then we'll work on specifics on your stocking plan/schedule - starting with fish to stock this Spring. If you have access to local puddles with YP populations, consider investing in a seine or fyke net to collect adult YP to help relieve the fiscal burden of stocking larger fish.