You'll have another one to add to your interactive map, Austin55!
Interesting history with their company and did a really nice job with the timeline in the link you posted. Now that you point out their corporate headquarters was located at 1226 E. Weatherford, I think that is where I first set eyes on that property and for some reason thought we had a discussion about it here but could have just been research. I spoke to Mr. Holland last year about the Chick-fil-A project on the Northside he owns the ground lease for that property where the gas station at the grocery store was located. He was super nice and explained he owns properties around Tarrant County because of his family's business as a Texaco distributor and is focusing the business more on ground leases like Museum Place, Northside and other real estate ventures as mentioned on their website. It is nice to see Fort Worth owned businesses thriving after all these years and finding new opportunities in other market types.
According to Google Street views, it appears they've been trying to do a ground lease on that open lot at 1200 E. Weatherford for at least 15+ years. I'm sort of suprised that something like a Starbucks, a small grocery store, What-A-Burger or Chick-fil-A didn't jump at that opportunity considering they're doing ground leases on the Northside. I guess it would depend on having the right franchisee lined up and market study for that side of downtown. The advantage of where the Sonic is located is that you can enter and exit going into and out of downtown vs on the other side of Weatherford it's ideal for those heading out of the downtown. In fact that Belknap bridge heading toward downtown has had a dark and sad history due to at least one wrong way vehicular homicide case that I recall from about 20-years ago (Christmas Eve.)
As far as these other structures for the residential project, I wish I knew more about them to form an opinion if tearing them down is a big deal or not. It looks like they've been around for a while but those two blocks began transforming to more light industrial sometime after 1956 per historic aerials and appeared to mainly be smaller residential prior to that. I look forward to seeing what they propose, I'm guessing it will be something similar to Cityscape Arts which they will essentially butt up against across E. 2nd St.