What kind of agricultural use would you like to see? Or do you just want the owner to keep it as open non-producing field and keep footing the bill. There' not much there, just yours and 1000's of other houses sitting on the rest of it so it's agricultural use is eliminated.
If you don't like what's going to be done with it, your HOA should have bought it and made it common area. I other words, if you don't own it, don't complain when the owner wants to use it. It's not a surprise....or shouldn't be.
The town can keep chemical plants from being built on it, but beyond that.......it's a slippery slope we all stepped on. Build baby build!

ADDED:
I think you're right in, "...whatever good it'll do". It's already cleared P&Z an there doesn't seem to be anything to stop it and no obvious opposition to it, even at P&Z. Were you at the P&Z meeting?
For anyone that's interested, I dug the minutes up from December. I was surprised the owner wasn't a developer, but a resident that's been on the land for 35 years. I feel for the few folks that are left having watched the gross amount of development trap them in. At least, I'm guessing they'll walk away with full pockets.... Looks like your HOA also provided a letter of support for it as well. Guess they didn't want to buy it.
http://www.flower-mound.com/agenda/PZar ... -12-11.pdfIt's item 11 and 12 for the Council meeting on Thursday.
"We must reject the idea that every time a law's broken, society is guilty rather than the lawbreaker. It is time to restore the American precept that each individual is accountable for his actions." - Ronald Reagan