Last plant I was in build T4 and T2 and you guys are talking roll back to T3.  Remember that every added option tends to increase cost of all the options and often results in less reliability and increased business cost since there are now more options to test.  I am just saying it is not a simple as you make it sound. 

Additionally, if you go back and review 40 CFR 50 NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS you will find that congress gave power to EPA to make amendments based on requirements and their duty to protect public health.  Go read the amendments and there are several examples of lowering the concentration values, several of which have the EPA determining no ill effect to the current standard at the time, but being forced to change later due to challenges that they had not enacted strict enough standards.  I.e. in the one case the American Lung Association sued the EPA for not requiring stricter SO2 standards at the time even though the EPA summurized that current level was not likely to cause issues for a small susceptible group with the current 5 minute limit at the time and given the exceptionally small likelihood of that particular group to be exposed did not necessitate a lower concentration limit; EPA lost the ruling and lowered concentration and making the standard stricter.  Yes the EPA is changing the standards, but that is what congress enabled them to do.  For the president to cancel the EPA he would first have to have Congress revoke the EPAs ability to change and then allocate it to another branch.  It is extremely unlikely Congress will ammend to give power to the president.