Just throwing something else out there;
Assuming that the UA is accelerating, what purpose does it serve to fulfill in the FE model? If the UA is real, then it itself requires some other hitherto unexplained mechanism to cause it to accelerate. How do we know this unknown phenomenon isn't accelerating the earth itself?
If you call that other mechanism UA, then why bother with all this "fluid" stuff? It doesn't really help to explain anything? After all, wasn't that the purpose of the UA proposition in the first place?