Okay, I know that's quite the term there, but it's more polite then "Screeching Autistic Horse-Cloppers", so I'm going with that.
The question is this: In an AU, if the circumstances surrounding a pony's life and upbringing change, the conditions that make them develop their personality and outlook on life, the skills they have at their disposal, everything. Does it make sense for their Cutie Mark to be different?
The Cutie Mark is supposed to be a symbolic representation of a pony's special talent, that manifests on their body. We know that it's inherently magical in nature, not a natural part of their biology. This is evidenced by the fact that Cutie Marks can be "taken", either by magic suited to the task (Starlight's Wand of Communism) or by simply draining ponies of their natural magic (Tirek giving the SUCC).
On the flip side, we know that the Cutie Pox can "give" marks and special talents, albeit in an uncontrollable and unfavourable fashion. This would imply that a pony's special talent is in some way a sort of natural, subconscious magic. It comes to them as instinctively as breathing.
ADDTIONAL NOTE: Okay, Officer Hotpants here just reminded me of something else: Cutie Marks can be swapped under certain conditions. We all know the episode where Starlight managed to swap Celestia's and Luna's marks, and in doing so they seemingly lost their own powers and dominions over their own respective celestial entities whilst gaining that of the other. Further evidence for Special Talents being natural pony magic, rather then a biological component.
So that's the point I'm wondering about: Is a pony's special talent something innate, or something they develop?