(...)
Edit: I also meant that it would take a lot of effort on Solas's part for my Lavellan to agree to help him. Even sans romance.
(...)
In my post-game head canon it always involves some of them saving each other life.
I admit though, thus I admire the people's lovely and amazing HC I read about here, my imagination on my PCs always limits to: "yeah, something, oh, this could be a cool scene, but when? why? and when...? oh, whatever, let's think of a cool scene and not really worry too much about the logical details". So: my Lavellan nor any PC has a background story, future plans, she's always a hero of the moment.
So as for potential future... Don't know... always imagine this somewhere in Deep Roads (I don't know why I somehow tend to turn into Deep Roads when I try to imagine the future ways of DA:I heroes. My intuition tells me all replies lie in Deep Roads) and...
Version 1: either Lavellan/Inquisitor gets trapped in some really dead end situation (no idea: cornered by countless darkspawn, meet face to face the new archdemon rising or sth of this calibre
) and then suddenly appears the Dread Wolf ex machina (who's exploration also brought in the area) in all his glory with new Flemythal powers and ideally shape-shifted and blows all the enemy party to hell.
Lavellan: ?!
Solas: Inquisitor, what are you doing here? (Thinking: This was supposed to be a path I was supposed to walk alone for eternity!) Are you all right?
Lavellan: I'm ok. Thank you for saving our lives, but I think you owe me some explanation on what the hell just happened here.
Version 2: our hermit apostate in a dead end, likely less darkspawn around (because... come on!), but generally "this does not look good" situation. Luckily, our brave Inquisitor explores the same ruins and gets on a right time to take opportunity to save the Dread Wolf's ass. They join forces in a moment and... yeah, that's a good start for a conversation, once all is over.
In both versions either epic boss fight, either a mindblowing cut scene
))) I know this most probably sounds extremely stupid - I appreciate I have some romantic inclination into crazy heroic moments, you know, help coming out of nowhere, storm and lightning, and ideally some sexy epic battle scene 
Gosh, if I could draw I would certainly draw something like this: always imagine a scene with shape-shifted Dread Wolf defending Lavellan unexpectedly from certain death.
Ok, just blew off some steam, hiding in my corner again 