On STA, they would be allowed 1250 watts fulltime with a suitable nondirectional antenna. I think the biggest day restrictions to a new licensed facility are WILS 1320 and WOBL 1320. WEXL 1340 is also a consideration, as well as WTRX 1330. None would affect a suitably located STA. Some stations have been using STAs for many years. I can think of one in Indiana that had 250 watts and a six tower array that is running with 62 watts nondirectional. As the relocation could be argued to be beyond the new licesnsee's control, the ratchet clause may not apply, and new rules may get rid of the ratchet clause anyway.
It's too bad the FCC site is down, and I did not save the radiation plots (thus, I can't do the math), but I suspect WEXL 1340 (its 25mV/m contour and WDTW's) was the only barrier to WDTW going 50kW-D/5kW-N DA1 by using their night pattern during the day. WDTW's night pattern was so choked in every direction other than about 15° Azi that 50kW into it would shoot less RF in the directions of WILS, WOBL, WFIN, WDPN, WTLC and WERE than 5kW into their 2-tower DA-D did. I strongly suspect (just might be wrong) that, with 50kW into the night pattern during the day, that their 5mV/m contour would have entirely passed to the east of the 5mV/m of WTRX on 1330 (especially if they were to use measured conductivity in Oakland County instead of the unrealistic 8μS/m in the M3 table).
Of course, that night pattern is THE major factor in the demise of WDTW.
If they were to build a new array a few miles south of the old one (thus further away from WEXL), they very likely could go to 50kW and have a "no complaints" signal over the whole high-population/frequently-traveled territory of the Detroit area.
Problem is, fully covering the Detroit area at night on 1310, under their 12mV/m NIF, is a distinct impossibility (unless WTLC, WIBA, WCCW, CIWW and WDPN were all to go silent - or WDTW could run 300kW into a ridiculous array with nulls deeper than the FCC would let them specify - like I said, impossible)
I'm still trying to figure out where the very brief operation may have been from. Since WDTW is still owned by Clear Channel (they seem to have been unable to get the FCC to transfer the license to MMTC), I wonder if they might have used the WDFN array, since they own it. Strange that the October 9th operation was after sunset. Running WDTW from the WDFN array during the day is simple enough (with 7 towers going unused during the day), but all 9 of the towers are needed for WDFN at night (yes, they could have diplexed, but that would be far more complicated than just going with a daytime STA).