This might not be improved much if at all under the above proposal, but it certainly wouldn't be any worse.
You're now saying UTC would be way better (not merely "not any worse") in this case. And I agree in this specific case. "1400-2300 from dates X to Y, 1300-2200 the rest of the time" is a tad better than "9-5 Eastern".
It comes down to how often one has to specify dates along with times. Of course, that stops being an issue if daylight tracking is also eliminated, but there are good arguments to track daylight.
Note: Your argument rests on the premise that UTC eliminates math is true. It's not true unless you only deal with people who also live somewhere that abandoned time zones.
Update: Added second and third paragraph.