I don't know what Disney's policies are, but I can tell you my experiences from working as a reservations agent for a large tour operator.
We had wholesale fares that had different cancellation penalties and different change fees than the 100% non-refundable/$100 (for most carriers) change fee. The fares were not guaranteed until ticketed, and once ticketed, had some type of penalty. They were less restrictive.
There were time restrictions, but we didn't have any for Orlando. Mostly the time restrictions were for Vegas flights, and there were pricing tiers depending on what time of day the flights operated.
You would have to ask WDW Vacations for the specifics. There will probably be some kind of change fee, but depending on what kind of published fare you find, it might be worth the cancel/change fee.
