Main Scenario Restriction Bloodstorm - Very Very Bad idea.

[Zojha]

And if the only way that they can have fun is by running end game dungeons for days end than as a good friend you will help them with the older stuff and make it faster.

You can't help players much with the MSQ. You can only help with the dungeons and trials, but those are probably the least time consuming part of it. You can't talk to Minfilia in your friends stead, you can't help with story battles (You even have to disband the group for them) and playing chocobo porter with a 2-seater becomes obsolete from 20 onward (Until HW).

They will have to do it on their own.