I don't think it'd be a great idea to simply skip the base game and the entire first expansion of the game. Well, perhaps players should be able to skip Heavensward (via a clever story transition from 2.x), but they should then have to enter Ala Mhigo at whatever level they are when they finish ARR. Also, if they were able to skip, how would the story explain away all the Scions new looks/ anything that happened that wasn't exclusively restricted to Ishgard?

If a jump potion is ever introduced, then it should level you to 60 but not let you skip story content. So, sure, you'd jump to 60 but you'd still have content gated by main story quest (unless you have a character that has already completed it).

That's just my opinion, though.