The key thing with the two existing daily rotations is the hub banks in DXB. Most of the Europe arrivals that get into DXB around midnight and early morning (especially the first flight) are timed to connect onto Asia/Australasia routes. A morning rotation in the UK has always been less popular for this. So whilst it's possible it doesn't serve the connections so well.
In fact Emirates have wanted to put the A380 into STN on one of the daily rotations, they even put slots in for S24 as a placeholder but there are capacity constraints locally at STN to really achieve it.