If I were you I'd negotiate a deal with my new employer: agree on the value of miles. It doesn't make sense for them to spend 30000 miles for a ticket that can be bought for $200, so come up with a fair valuation of the particular airline's miles and say "if the ticket works out cheaper, I'll have a proper ticket. If it's cheaper to go with miles, that's what I'll do." So they get a good deal and with a bit of luck you will be able to reach some kind of status and enjoy FF perks some if not most of the time.