Well I’m going to bump this from last year with an “I told you so” to the question of “I’ll be sure to come back here if I need any help listing all the reasons something can’t be done that has already been done” and reiterate what I said in my original post:
Reverse engineer the most popular 2 wire commercial sprinkler system on the market and produce a compatible controller that works with all their valves, and that way the greenskeeper can buy all -their- valves and the cheapo controller.