The requirement for the Seychelles air law exam is only for the A320 drivers, as all other aircraft including the A321's are VN registered. So you need a Seychelles license if you fly the A320's.
Take it this way the agencies all try to keep their costs down and that's what they could do for the last months or years. I am sure this will change in the future. As far as I know the beautiful islands of the Seychelles are a destination that's hard to reach and so it is very expensive to get there. I have heared that you have to spent about US$ 1000 to US$ 2000 for this event.
Regarding the salaries for the different fleets I can confirm the numbers stated by "Lost in Saigon". It seems that the folks on the Airbus and on the B777 get slightly more than on the B767.
Regarding the possible upgrades from B767 to B777 I don't belive this and I never did!
Take it this way, the story was brought up to keep us here. It's like the carrot you put infront of the nose of a donky to keep it runing. That's what they are looking for. The B777 is the biggest ship and this will be flown by local in first place. Take a look at the ads looking for B777 captains, so you see they are looking for rated chaps and are not realy interested in upgrading one of the expats.
For those who are interested in joining and coming from a place far off the HVN route network be aware that the travel problem, meaining being off loaded from a flight you have a "confirmed" ticket, occured again very recently and not only once.
Further to this one pilot was stuck in Paris getting back to Vietnam for a couple of days. As far as I know he never got reimbursed for the expenses he spent for hotac in Paris.