Yep start making the CS series again!! S&W knows they would sell for sure. They sound more reliable than some of the latest offering and with less headaches.
If only the TDA guns were more marketable among today's newer shooters who want SA-ish light triggers.
The improved and tighter machining tolerances of today would likely make 'filing/fitting' extractors unnecessary. We were seeing some of the late production (2010-ish) 3rd gen guns where an extractor could be dropped in and fall within good spec, and it didn't take long for the requirement of buying a .40 extractor bar gauge to be dropped in the M&P pistol armorer classes. (They never even offered extractor bar gauges to armorers for the 9's & .45's, as they concluded the tighter tolerances made them unnecessary, and the 9's and .45's came along after the .40s.)
That would just leave the sear release lever to be fitted for each gun.
I'd also like to see them replace the solid extractor pins with the roll pins they were working on in the last days of the 3rd gen guns. I never got around to calling and getting the tentative list of roll pin sizes for the 3rd gen guns, which we were told they were developing in the Repair dept. Oh well. Maybe a coil pin?
Or, corporate might have a brain bubble and decide to offer a rebirth of the 3rd gen guns in one of their previous DAO variations (which would never interest
me, FWIW).
Personally, I'd like to see a trial run of compact and subcompact "4th Gen" TDA guns offered with both aluminum and steel frames. I'd jump on a steel-framed 3913TSW & CS9 so fast my credit card would be steaming. I'd even buy an all-steel 391
6TSW if it came with an integral accessory rail.

I might even buy another 4040PD or 4013TSW if steel-framed version models were offered. No full-size models, though, as they were belt-mounted boat anchors over the course of a 10-18hr shift.
Day dreaming ...