I think the surviving Grey Warden idea would be the smoothest to deal with. Without the Treaties in their possession, they would be relying on word of mouth as well as instincts. I'm sure at some point someone is going to say they ran into other Grey Wardens, which would pique the interest of our group, which is why I do see them wanting to catch up/cross paths since they'd know they'd be more effective together than in two groups, but again that is probably something for a later event. And I do think it's possible to recruit grunts from Loghain who have gone AWOL, if that's a role you're interested in taking.