Estinien in story

[Lukha]

Wasn't part of his arc in HW learning to deal with working in a group, though? He was more or less a solo actor despite technically being a part of Ishgard's military up until he decided to travel with the WoL's party in Heavensward, and I felt the story made a point to show that he was softening towards them over time.

As he is currently, he's really perfectly poised to join the Scions for several reasons.

1. Two people with whom he developed pretty close relationships are members, and he was shown in SB to at least be thinking about them, even if he was probably mainly motivated by tracking down Nidhogg's eyes. I forget the precise line, but when he destroys the canon he mentions the WoL by 'name' ('aibou', or partner, which is the epithet he uses to address the PC in voiced scenes).
2. He really shouldn't go back to Ishgard anytime soon; he attacked VERY publicly and there's likely to be a lot of resentment towards him for that. I'm sure Aymeric and the WoL would do their level best to make sure people knew he wasn't in control of himself at the time, and it wasn't his fault, but chances are it just isn't safe for him there right now.
3. The Scions need an Ishgardian representative. Every other major power, including Garlemald, has at least one person in the Scions to represent it. Even if the reps for the three original city-states were technically Sharlyans who happened to be working out of those areas (which also brings up the point of whether or not they're going to introduce someone to take over the Gridanian slot).

If he's still interested in making himself useful after finally destroying the last remnant of Nidhogg's power, lending his considerable strength to the Scions would be his best option at present. Of course, he's also done quite enough by anyone's standards, so I doubt anyone would blame him if he wanted to go find himself a quiet corner or Eorzea to settle down in and just farm popotos or raise chocobos for a while.

[Theodric]

One of the major issues is that there's a rather bloated cast at the moment where the protagonists are concerned. We rarely have the main cast on screen together at the same time as a result - Y'shtola, Krile and Thancred were only present for a small portion of 4.0's MSQ's, for instance. I also have a hard time imagining someone like Estinien getting along with someone such as Lyse - he was very quick to point out the flaws in Ysayle's actions and line of thinking but would he do the same where someone like Lyse is concerned? If he remained silent, would it be true to his character or would it be plot convenience?

I liked the little adventure that Alphinaud, Arenvald and the Warrior of Light embarked on back in 4.1's MSQ's. I could see something like that happening with Alphinaud, Estinien and the Warrior of Light. With that said, though, 4.2 is almost certainly going to focus around the aftermath of Doma's liberation so I do not expect to see Estinien show up in anything other than a teaser during that time.

[Alleo]

Cant I just make my own band of NPC adventurers and leave the scions? I could totally see Alphy, Alisea, Estinien Arenvald and my character as an awesome band of adventurers. (Let a girl have her dreams q_q)

I only want him back in the story and with the scions if that doesnt mean that they will kill him for some emotional impact...if that would be the end goal for him than he should gladly just stay out of the story and be save. Maybe he could be the link between the scions and Ishgard without completely joining both sides thus still staying free of it?