Using one of the options at Qld BDM online, Elizabeth Jane BLAIR died 23 July 1863
Nope, I am not forming the view that Gordon was not without blemish, but so far, I have not seen any evidence to suggest he was hiding secrets from his Scottish past. The easiest way to hide skeletons in the 19th century when migrating was simply to change your name after you landed. There was no formal process required. You did not need to prove your name to anyone, and you simply got on with life under your new name. You could write home to Scottish relatives and perhaps say "out here in Qld I am known as Gordon BLAIR" when in fact back in Scotland you had been known as Donald M'DONALD. There's so much difference in age between the passenger list and your other sightings, that it is of course entirely possible that the 19th year old lad, Gordon BLAIR has no connection to your tree.
Re females retaining their surnames .... in NSW during the penal era, and particularly under Governor Lachlan Macquarie, females (convicts, and those who came free) were often recorded under either name. Macquarie was a Scotsman...
Scotland is not the only country (I think of Spain) , but here's a thread re Scotland -
http://www.rootschat.com/forum/index.php?topic=454431.0JM