Hi Striker26,
in all honesty, I can't give you a definitive answer because I don't know. The Qatar MPL is so new that people aren't at that stage yet or are just achieving their 1500 hours.
From the information I could get, you'd have to redo the theory exams via distance learning and to achieve your CPL, I had it suggested to me that you come back to the UK for 3 weeks or so as a 'holiday' and do it then. It's highly unlikely QR would give someone the time off to redo their exams/CPL so they could move away from them.
As far as changing type, i've heard that it's fairly easy to transfer across the QR fleet. I've heard some people did it within 3 years so in that respect it's fairly good.
I'm still asking around to get as much information as I can so anything else I learn i'll post on here.