I don't think there is an upgrade program in place at the moment with Scoot, all Captains are direct entry. There will have to be one in the future but not sure when.
The hours and sector requirements could make it a long wait for an inexperienced joiner as the B777/B787 isn't normally the sort of aircraft you'd get your first command on unless you're with SQ, CX, EK etc.
Joining a low cost with 200 hours and upgrading at 3000 hours onto an A320/B737 happens all the time, I not sure if it would happen with widebodies.