Nothing really to base a strong opinion on here. No details, no plans.
So... I guess I support DoT "considering" domestic testing because they should be considering all options for containing the pandemic and ensuring a safe travel environment. Hard to know if something is a good idea or not if you don't seriously consider it. Get back to me when there's a plan. Or when they say, "We considered it and rejected the idea due to X, Y, and Z."
My gut feeling is that any version of domestic testing is too little, too late, for the current outbreak. Policy process, rollout, vendor and consumer education; by the time that's all ready the facts on the ground should be very different. But, by the same token, going through the policy process--even for something that ultimately isn't used--would be a productive exercise in preparation for future pandemics.
...or in case the global community has screwed up this pandemic response so badly that a novel variant is already lurking and ready to hit the reset button on everything.