I'd like to see a lot of attention paid to accoustics. If Fort Worth had a great concert venue, it would be the start of something new for Fort Worth. I doubt you'll ever see an NBA or NHL team in Fort Worth, but you should design it so you can retro-fit luxury boxes at a later date if needed.
Capacity of 12,000 sounds fine to me, but I have no frame of reference. Rather than comparing it to average WNBA attendance I think you need to compare it to similar facilities in markets we would compete with. You don't know what the trends are going to be in 10 years, but these facilities hang around a lot longer. You know they'll be around in ten years and these are the facilities we'll be competing with for shows, teams, etc. Maybe 12,000 is the number and maybe it isn't.
So I get back to accoustics. This is something we can control that pays immediate dividends and never goes out of style.
On your first point I would have to respectfully disagree, if you are referring to rock music concerts. It would not be the beginning of something new, it would be the return of Fort Worth as the premier concert venue for north Texas. In the early days of RnR really big shows were wherever the expected crowd could be accommodated, no regard for acoustics. The Beatles played a baseball stadium in NYC, and Memorial Auditorium in Dallas. Elvis played in the Cotton Bowl. Hendrix at Will Rogers. But when the TCCC Arena was built most of the serious shows went there. I can remember the Stones (Lotus Stage), Led Zepp, Tull, Floyd, Deep Purple, Diana Ross, Springsteen, Supertramp, Santana, the touring production of Jesus Christ Superstar, McCartney and Wings, Dylan and the Band, etc. all choosing Fort Worth over Dallas; probably capacity had a lot to do with it since this all seemed to end when Reunion Arena was built in Dallas. But Dallas had venues before Reunion, and they were all like big cattle barns, and they still are. Reunion and ACC both had/have terrible echoes, especially in the balconies. The round TCC Arena didn't. The Yes shows using the revolving stage-in-the-round, and the quadrophonic Pink Floyd productions I saw were unequalled in my concert-going experience for superb sound, and this was all pre-digital. One has to take into account that the music scene today is significantly different than back in the 70's. Back then a lot more fans actually went to concerts, it was a much bigger deal than for fans today. The ridiculously inflated prices of tickets probably has a lot of do with that, and with the fact that the biggest concert draws in the 2010's are some of the same that were touring around in the 1970's. Many of the newer bands, even the really successful ones, play clubs.
I absolutely agree that size for size sake is not the best criteria to use when building an arena. The projected uses have to be considered, and they are not likely to include NBA, WNBA, AFL, or any other non-collegiate sports events other than wrestling or an occasional pre-Olympics indoor events exhibition or competition. Of course building an arena of any substantial size for the stock show rodeo, an event that lasts three weeks per year sounds pretty silly. Building in naturally fine acoustics would make the arena more marketable the rest of the year.