For the record, I changed my vote. I’ve been riding a lot during the weekend, and I’ve come to the conclusion that there is nothing useful about the mount being a follower. I like using it for the sheer fun of mounted combat and for getting between certain points faster than usual, but I’m convinced there’s never going to be a situation in which I would want to use it to fight something, instead of a pet or a thrall.
Having said that, I still think it would have to count towards the follower cap, for reasons I outlined elsewhere.
Finally, I still think this is a moot point. The technical difficulties and the possible imbalance make this so risky, that I don’t think Funcom will do it. Heck, I don’t think they should do it, given all the bugfixes and tweaks they have to work on.