What you're saying doesn't make much sense. Firstly, customers choose this option because they don't wanna risk anything. Secondly, the 2 year warranty isn't the only thing Ford offers if you service your car during that period (and no COBB tune for iunstance), but when the warranty is up and the car breaks down, Ford is more open to compensate.
Sorry, I think you may have misunderstood my post. I am referring to the decision making process a Fiesta ST owner goes through when considering their available tuning options. Typically, an ST owner would only consider the Mountune MP tuning kits if they would prefer to not be concerned about having issues when utilizing their car's factory warranty at the dealership or with Ford. The MP215 is more expensive, offers less gain, has less support (only comes with one map), has less gauges, etc. and again, it cost more than the competition. Plus you have to pay to have it installed.... so it's real value/benefit is only the fact that it doesn't impact your factory warranty.
If factory warranty is not a concern, typically an ST owner is going to go with one of the other tune options such as Cobb, Mountune's MR, etc. as it's cheaper and usually offers better gains.
With that in mind, your factory warranty starts from the day of purchase(so to speak), so ideally the best time to get an MP kit or a tune that is covered under factory warranty is as earlier as possible or rather with as low mileage as possible (so that you maximize it's only real benefit or value vs the competition)
In my mind, I'd wager:
MP215 purchased at a dealer and installed by the dealer (therefore not impacting your warranty) at 0 miles is better than:
MP215 purchased at a dealer and installed by a dealer at 25,000 miles or a year/2years in to ownership.
The MP215 kit (installed by a dealer and at a dealer, keeping the factory warranty) begins to lose it's value the more miles you put on your car vs. the competition (other tunes) as they are not covered under warranty in the first place, so mileage or length of ownership, doesn't matter for them.