An Aston DB9 or Rapide would make a better DD for the suggested use case...
Or a DBS. Underrated car. For heavy or regular traffic, a torque converter auto will always be better than an automated manual. I would still take a 612 though, making sure it had MPS4Ss for surface water during those Gulf rainstorms down there. A 612 looks huge in the UK, but I guess not so much in Texas.