I know that there are objections to opening ishgarde for lore reasons but surely that is preferable over level up potions? Even with early access to Ishgarde there would still be alot of limitations with what you could do there without catching up in the MSQ. For example no access to external heavensward areas(western coerthas etc) and no access to 51+ quests. I found the 30 level jump with DRK/MCH/AST jarring; 50-60 levels is even worse. One of the main complaints is that players can't access DRK/MCH/AST from level 1 at each city state; so give it to them. Place an Npc to introduce players to the jobs from level 1 and then prompt them towards ishgarde at level 30. You can still let players access the jobs from level 30 onward and new players can start as the job they wish from level 1. I know this presents some plot holes but it wouldn't be the first time SE altered cutscenes depending on a player's choices; like the Azure Dragoon dialogue in heavensward.