It's doable, while the region is far less accessible for ERE, and that the abandon by the administration (instead of only emperors moving from different centers) would be still huge problems.
With, as you noticed, the issue that Aquilea was right in the way of raid and romano-barbarian campaigns. While it makes the city a perfect place for a QG (as Marcus Aurelius used it), it's far more perillous for a whole administration. (Without mentioning the problem of walls : they were destroyed by Huns in the 450's)