Request: Option to mix multiple Players and Trust NPCs in one Party
a) I know the developers said, when Trusts were introduced, that the AI relies on having only one player character. However, they also said that it was not possible to find the resources to develop Male Viera and Female Hrothgar so... "Times change."
b) Director Yoshida has once also said something along the lines that he was excited by Trusts because he wanted to give Final Fantasy fans the option to play FFXIV as a single-player Final Fantasy story if they wanted to.
Therefore, I don't think that letting players run parties of 2 Players + 2 Trusts, or 3 Players + 1 Trust, really violates the spirit of the design intent, since it's already been established that the developers are "okay" with players not wanting to PUG story content.
c) As for my personal motivation: I enjoy playing with other players, but I also play FFXIV with a friend in a different time zone. Sometimes, we're both exhausted and we want to do some content together, but neither of us feels up to being in a situation where we feel like we have a performance responsibility to other people.
Also, sometimes we just want to relax and spend time with each other at our own pace. Either to just stop and casually chat when we feel like it, or because we want to take in the lore and sights of a duty when seeing it for the first time. But we can't do these things in a full party of players, because neither of us wants to be inconsiderate to actual people.
And of course, duo'ing more recently-released duties may technically be "doable", but only with certain Job combinations, and it's quite slow. And some mechanics simply do not behave workably when both under-sized and level-synced. And it negates many of the rewards, such as EXP. And it's not even an option for "current expansion" content, since "Undersized Party" is disabled.
d) Personally, I don't think that this is anything close to the highest priority that I expect the developers to be focusing resources on, but I also cannot expect something that I desire to ever actually happen if I don't tell the developers that I want it... so... here I am.
To summarize:
I, and the friends that I play with, would enjoy it if the Trust system was expanded to allow for mixing variable quantities of Players and Trust NPCs.
This way, there would be much more flexibility in how groups of friends might approach the story and content experience of FFXIV.
For example, if 3 friends want to level together, but do not feel confident about gameplay mechanics. Then they can just relax and make Alphinaud deal with it.
Or, if 2 friends are tired and know that they will probably make a lot of mistakes, and would like to feel free to stop and chat while completing a few Dungeons at their own pace. Then they can rest assured that Thancred and Alisae don't really care.
...And so on.
e) I think that this would also help make Trusts, and leveling up Trusts, a less isolated and "lonely" experience. To be sure, some players must enjoy that they can enjoy a Dungeon entirely alone, at their own pace. But other players, such as myself, might find the very silent and isolated feeling of Trusts to be somewhat stifling, and that doing it with a friend or two is more enjoyable.
f) As for how it might work mechanically, well, I would imagine that it is all decided by the Party Leader, like most Party configuration settings. The Party Leader would decide which Trust NPCs will be present in the duty, if the party is currently undersized.