You asking for quite a commitment there. That's an awful lot of hours of gameplay that has to be coordinated.

What happens when your co-op partner is online and you're not (or vice-versa), are you going to mothball the character until you're both on together? Sounds like a long process.

In our guild, we'd usually quest with whichever members were at approximately the same level and stage of progression. If anyone was stuck on something, someone would jump in to help out (where possible). Most members have alts at various levels, so there was usually an option. But generally people would go off to follow their own path in the interim (which would result in them clearing an area, preventing them from joining someone else in an instance that wasn't cleared).

There's plenty of group content in the game... Cyrodiil, group dungeons, trials, Craglorn, etc.

I genuinely wish you luck in finding someone to commit to questing the whole thing co-op. I think you'll struggle though.