I gather that Merryfield is actually rather busy these days with RN (and AAC?) rotary training activities. Difficult to coordinate with UAS requirements. Also the present day locals are very anti any further aircraft noise. Whereas when I lived there many years ago, people were pretty tolerant of the Vampires, Canberras, Wyverns and Sabres. As well as the FAA's Sea Venoms a few years later whilst Yeovilton was being prepared for the Sea Vixen. Of course it was manna from heaven for me, living less than a mile from the RW threshold!
Little in the way of permanent buildings and with a travellers' site where the old Westland's hangar was in the 1950s, probably quite a bit of investment would be needed to accommodate UAS/AEF flying.