I was going to respond earlier, then decided not to, but okay, let's put a few thoughts out there:
1. According to Google Maps there is a name for this neighborhood besides "far southwest downtown." It's Sunset Terrace. Interestingly, the only three single family homes in the area are in the parcel for sale.
2. I think it would be more attractive if Daggett were extended between Sunset Terrace and 11th Ave., providing non-freeway access to the area from Summit (not sure if the right-of-way could be secured although it looks like it might be there on Google Maps).
3. I know that sometimes water treatment plants can give off strong odors. If this one does, I don't think this land is suitable for any kind of residential or retail use. Who would want to go to a stinky neighborhood? The prevailing south winds would carry any odors away from this spot but on those occasions when it swings back out of the north.... Pew!
4. Putting one apartment building there will not make it a "viable neighborhood." I think to do that, there would need to be more land available for development... I'm thinking of the parcels bounded by Broadway & I-30, and 11th & 14th Aves., and also by Broadway & Daggett, and 11th & 15th Aves. It looks like the latter parcel is a City of Fort Worth maintenance facility. What would really make it viable would be to clear out the industrial buildings between the parcel for sale and Forest Park Blvd.
5. If all the parcels above were cleared for development, I would suggest extending Broadway, Daggett and 15th Ave. to Forest Park Blvd. and make that the "front door" to the neighborhood, with a light at 15th and Forest Park (it looks like there's already a break in the median where 15th would intersect Forest Park). I'd leave the median intact for the other two streets, allowing for right turns only in and out. Allowing left turns along that bend, especially with the I-30 exit right there, could snarl traffic.
6. Extend 15th Ave. west of Forest Park, but as a bike trail only, and connect it with the planned east bank Trinity Trail. Having easy access to the trail could make some light retail and eateries along Forest Park viable.