Asked this question a few years ago, I would've said I'd had zero interest. My preference has always been that they focus on building a deep and satisfying offline single player mode before expanding to online.
That preference remains the same today, however I've lost all confidence that EA will provide a satisfying, deep offline experience. Ever since they switched the system from MM to CM, none of the major features have truly impressed. Player growth is just the most recent example of a shallow, poorly conceived and implemented feature.
So maybe an online CM is the way forward. I don't know. But I wouldn't want an online CM that's dependent upon playing with friends, because as someone who's in their 30s with fewer and fewer "gaming" friends, that'd really suck. Just like Destiny sucks for us older folks who struggle to coordinate gaming time with friends.
I'm also not a fan of an online CM mode that would require playing multiplayer, as anyone who's played Seasons or FUT multiplayer can attest to how bad that experience can be. Plus it'd just give further excuse for EA to not emphasize improving the quality of the AI and single player gameplay.
Personally I think I'd rather see them introduce microtransactions or some type of money-making device to fund CM development. I play FIFA hundreds of hours over a year's time, so I have no problems paying a little extra for a better single player mode, while we can clearly see the benefit that FUT's cash-making quality has on its priority for development.
In the end, I'm not as opposed to the idea of an online CM as I was a few years ago, but that's less about excitement for an online mode and more because I'm just frustrated by the lack of CM's progress over the years.
(And if we're talking about favorite single player experiences, my favorite is still PES's when it was at its peak. I'd rather EA model CM on that than any online modes. Not to mention I'd take PES's new chemistry system over FIFA's new player growth feature any day.)