Does it have to be the MiG-15? No, it doesn't have to be. My thought is just this: with which other airplane would the challenge be equally fun? The MiG allows you to slip out of the bottom end of the Aletsch canyon with >500 kph, and this means you can still gain some substantial altitude for a subsequent descent covering a few kilometers to the next airstrip. Of course in diverse hangars there are other planes with questionable variants of alternative physics. With extreme gliding performance you can reach any runway but then the landing procedure is completely unrealistic.
Actually, i find both flavours of the challenge type very fun: (a) engine out scenario in smaller or bigger airplane from initially less or more altitude and with less or more distance to cover to reach a suitable runway, or (b) speedrun along mountain slopes + engine-out landing.
Getting once more deeper into topic (b), given a certain speedrun line along mountain slopes, it's actually a challenge to find "the right airplane" to make it challenging and fun. A plane with little drag and good glide ratio may make the challenge boring, while a plane with less ability to build up kinetic energy (like any small or slow bush plane) or more drag & energy loss in the turns (like F-14, F-15, F-16) will make it completely impossible to complete the line.
At this moment, I'd have two questions:
1) Is it possible to prepare an engine-out scenario file with airborne initial conditions?
2) Which plane would you guys put on a list of favourite engine-idle speedrun planes?
Footnote on the engine-out topic: With the MiG-15 you have to start modding the airplane code if you want to have a longer engine-out flight time on battery power because the authors set the battery time to less than a minute. What they had in mind was not unpowered landing, but knowing by hart the in-air engine restart procedure. So, you simply cannot do any unpowered flight plus landing unless you're within 1km and low above the runway.