Been running this idea through my head for a wile.

Basically, it is the idea that you did -at the very start of your adventure- join the adventurer's guild. So, instead of the current set-up, maybe have it optional to use alternate characters that are from the guild. This system would have a couple of twists to it not used in current Trust/Duty Support.

First, as stated, you would have options for members to fill in for each of the party roles. Maybe not a massive number, but enough to get you going. As you progress through the MSQ and various sidequests, you run into other NPC's who are either inspired by you and join the guild themselves to become adventurers, or those that decide you are worth partying with due to your reputation. Whatever motivates them. Kind of like the Adventurer Squadron, where you have random npc's want to join up based on what challenge log stuff you complete, except guaranteed due to completion of the appropriate quest.

2nd part is as you use these npc's, they earn what I will call for now companionship levels/points. The more you use a particular one, the more they get. Pretty obvious. What this does is at the right points (character level/msq point/companionship level -combinations) opens up story quests involving said characters. You could even have combined ones involving multiple npc's. This would be nice on a lore standpoint, giving the player something for using the system, rather just the ability to not wait in a queue.

One of the fun parts of this is the potential variety of NPC's. Imagine running a dungeon with various members of the tribes (like a sylph healer, kobold bomber, and a Sahagin lance user) or countless other choices. Could be very entertaining at the least, along with the aforementioned lore aspects.

That is the basics anyways.