Regional jet pilots transition onto airliners quite easily, turboprop pilots understandably take longer. A realistic timeframe would be at least two years in the right seat before a Saab Captain would be ready for command on an A320/B737. CASA and the insurance company would need to be satisfied with the program as well. There would also be a need for experienced first officers to baby sit the new upgrades for a month or two after release to line. Certain airstrips may have restrictions on them such as minimum time in command or on type before operating there. There would be a further wait while REX pilots gained the experience necessary for check and training approval.
They would need to have "expats" on the payroll for a fairly long time.