I used “powerlevel” here as a catch-all term for character level, item level, and consumables, whatever makes a 5-person group able to hold their own in Molten Core. For instance, if the group decides we care about items found in MC, we may intentionally keep the item level of our equipment low, as to make items found there relevant not only ICly but also mechanically. In that hypothetical situation then the group would instead use character level and/or consumables to make up lost ground.
Personal quests would want to tie in with activity that rewards EXP. For example, a disciple of Naralex’s quest could be to wake his master (again) and to study the other oases of the Barrens.
If they want to design and DM, definitely. But my thinking is the sidequest should at least be related to that party member, to give everyone’s character a time to shine.