Makos forwards Shannon Frizell, Pari Pari Parkinson and Tyrel Lomax join McKay, while Counties prop Kalolo Tuiloma, Counties outside back Tevita Nabura and Wellington midfielder Thomas Umaga-Jensen are also new.
Otago first five-eighth Josh Ioane is the other new player, and will cover Lima Sopoaga and Fletcher Smith in the No 10 jersey.
There is no space for former Highlanders co-captain Shane Christie, who didn't play at all last season due to an "illness".