I am aware of several 'experienced' Aussie turbo-prop drivers (5,000+ hours, C & T, ATO etc), that are quite keen to make the move onto the ATR aircraft when they arrive. They all have multiple turbo-prop endorsements and a fair bit of EFIS time, some on types that fly a fair bit faster than the ATR too - however, none of them have any ATR experience.
Over 20 years ago, I was given Command training on the ATR42 before being employed on contract, and only bonded for a year. Had just over 2,000 hours on Metro 2, 350 on Bandeirante, and about 300 on Nomad at the time - and that was in Single Pilot operation. Did my Multi-crew training during the endorsement and Check-to-line. And scored a 3 day refresher course at the factory simulator at Toulouse when I went back after a break for a second contract. Long way from the South Pacific to Toulouse just for three days.. But it was on French Government Aid money that had to used up by the deadline time or was lost, so it didn't cost the company anyway.
So don't think of them as complicated, or inferior to jets. They are just the logical progression for Regional and Outback connections from the Chieftains, 402's, Metros and Bandeirante's of yesteryear Commuters.
With training, any Aussie turboprop or piston twin pilot could get a look in if Company management had the policy, without resorting to selling out the locals and importing foreign drivers.
Straightforward differences course only for the -500. (The 600 is a different ball game, but will be for -500 rated crews too.)
Now those 600's that are coming would be fun on the Regional routes. - As long as you don't have Jet P3nis envy, and can take the jibes from the Dash 400 drivers about speed. Won't matter much on the shorter, high frequency routes anyway.