it’s time to start asking why.
Because it'll be bloody expensive. And don't say "then try paying for an accident". That's a theoretical. Actually building, manning, and running a TWR (and more than likely the extra associated low level E sector) will be a not inconsiderable ongoing cost (at government rates). While costs are recouped from the airlines via charges, it will not be possible to directly target BNA pax, so there would have to be a whole negotiation with industry as to any wholesale increase to cover those costs, with associated drawn out to-ing and fro-ing about cost benefits, and risk analysis, and all those previous studies by ASA that show one is not needed, so what's changed etc etc. I'm pretty sure they would not just absorb them. In ye olde days, the government had deep pockets. Now you have a cost conscious, stakeholder return driven business running things.
Infrastructure is expensive, and once you commit, you are stuck with it. Witness closed million dollar TWRs at Gove, Wagga, Port Hedland etc. Airlines are fickle beasts. They demand demand demand, then will drop something without a moments hesitation. That's why airports don't build things until they really really need them. You get burned by airline forecasts and industry promises a lot. Look at TMW, they'd never build a TWR there now, yet they've still got one to keep nothing but small turbo-props and bug smashers apart, and BNA doesn't, with 180 seat jets.