He also had a war table mission in DAI. They're definitely keeping the guy around in the lore for some reason.
It wouldn't surprise me if Solas has non-elves working for him, likely without even knowing they're working for him. I wouldn't put it past him to have a Red Jenny-eqsue organization at his command that involves non-elves. If someone had figured out how to manipulate Red Jenny, the potential for abuse in that kind of anonymous setup Sera had was ridiculously high b/c the individuals involved are so in the dark about the consequences of their actions. Due to that, they're basically a loaded gun, waiting for someone clever enough to figure out how to direct them to tell them where to "point and shoot". He could easily set it up so no one even knows who it is that's giving the orders.
Frankly I'm surprised the Red Jennies aren't already used by Thedas' nobility to take out political rivals. It seems like an incredibly easy thing to do, just bribe a few servants into saying Lord Something-or-Another beats his staff, and boom, Jennies do him in.
...Or maybe they already are widely used to do that. Sera doesn't seem like the sort to investigate thoroughly.
In the main game he was humble and discrete, but in Trespasser, look at that armor! In Trespasser he's strutting around in some kind of anvient elvehn armor no one has ever seen before, that shines like the sun. He became an ostentatious man.
Although...I guess he's mostly hiding in between the eluvians. He was besieged by Qunari only because they had found access to the Eluvians. He won't be walking around Val Royeaux, he'll be untouchable as he will be in the cross roads and various lost places disconnected by Eluvians the majority of the time. That works.
Solas was ostentatious in Trespasser because he needed to be. He's a smart dude. He knows when a situation calls for theatrics - such as when you're going to route one adversary (The Qunari) and reveal yourself to another (The Inquisitor.) His attitude in Trespasser likely wasn't his natural personality so much as an attempt at intimidation. You can see that attitude in Haven, when you ask him his opinion on the all the Herald business and he says "posturing is necessary." He recognizes that sometimes you've got to show off a little. It can help win allies and demoralize enemies.
(And on a meta level, this is probably the reason why the writers had him show off - it wasn't just Solas trying to intimidate the Qunari and the Inquisitor, but the writers trying to intimidate the player as well. If they had Solas show up in his raggedy pants and jumper, doing nothing of note like petrifying entire armies, I don't think his appearence would've had quite the same impact. It'd be easier to dismiss him. Trespasser as it is, elven armor and Qunari statuary included, proved him to be a serious and overwhelming threat.)
But Solas knows when to keep a low profile as well. He kept one in the Inquisition, because he needed to - all he wanted was the Orb, and if he went around showing off all he knew and was capable of, he'd probably be targeted by Templars or the Venatori (Not to mention it'd make any future deceptions harder since everyone would know who he is.) Right now, I imagine he's being a bit more selective - he'll show off to certain enemies like the Inquisition and the Qunari, and maybe to potential allies like the elves. But he probably recognizes that it's better to work in secret. Strutting around Thedas in gilded armor shouting about his plans for the apocalypse probably isn't his go-to tactic right now.
His ultimate goal is overthrow the current order of things. So he's not going to try and ally himself with the powerful and the secure, because they're benefiting from the current order. With them, he'll be humble, he'll be secretive, he'll try to keep beneath their notice, because they're enemies waiting to be made. Instead, he's going to try and recruit the disenfranchised: Elves, apostates, runaway slaves, maybe even Tal Vashoth. They're the ones on the bottom rung of society's ladder. They have very little to lose and very much to gain from drastic change. So if he shows off to anyone, it'll be to them. This is also probably why he was in that armor in Trespasser to begin with. Like you said, the Crossroads is his place. His organization is largely based there, I'd imagine. And he has to show off to them, to assure them of his power and capability. It's a way of building morale, in the same way that the Inquisitor had to put on so much pomp and circumstance when they took over.