I think it all makes sense:
Simon Dawson is
- somebody roughly their age (who, eventually, won't claim: "I'm the last remaining Maiden member" in around twenty years)
- somebody they get along with
(a characteristic that is-I think- more accurate than "being Bri'ish")
- somebody who won't have to play much lower or higher than his level. (e.g Mike Portnoy toured with Twisted Sister, which was fine, but it wouldn't have suited studio work) - that's why Simon Philipps -great as he is- would have been a miscast.
- somebody who is a team player, not a star drummer, and has been tested prior in another band.
His recruitment (albeit on a temporary basis) may remind one of that of Janick's after all.