I think we'll just agree to disagree here. I just can't see it happening at all. Plus, Saints Row doesn't have choices that have an impact on subsequent games, unlike ME and DA. Each SR games stands on it's own. If there was a way to do it like ToR, with customizable player characters (within the human-only PC in this case) and every player getting at least a chance for input, then I'd probably be more open to the idea.
I'm not against the idea though. If they can do it in way that doesn't involve taking control of a squad mate, I'd support it. I don't think the idea is a bad one at all, and I do miss that form of gameplay in RPGs. I don't consider SR the same kind of RPG as ME and DA are. Note that I do think SR is a form of a RPG, but quite different form the setup of DA and ME. As it is, I think we'll get co-op MP again, with a separate SP campaign.
BioWare hasn't done SP co-op since NWN, and I can't see them taking away dev time to add this. I don't think it's a waste of time, but given that BW can have problems with getting music into their non-story zones in DA:I due to resources with the year extension, co-op is very unlikely. (Immersion my foot, I know it was the music not being considered a priority for resources. It still makes me quite irritated.)
I can see why it's a request though, and if they can do it, then I'd be happy with it. 