I think the idea for the vehicles is awsome. They're completley customizable and although they will probablly replace Mumbo transformations (no more washing machine) this is the kind of change that can bring platformers back. Ratchet and Clank attached themselves to shooting, Jak attached to sandbox, Mario is created by a crazy man no one else can think like, and now banjo is attached to custom vehicular combat.
Mario taught me one thing with galaxy, the only time I enjoyed it was when I was doing something new. Collecting the coins at the end just to get Luigi felt like video game boot camp. Just returning to spiral mountain in fancy HD would have been boring for the new Banjo. We would have got all excited for it, and then realized it was a let down (Twilight Princess style)
If this was announced as a new IP everyone would have instantly fell in love with it. As long as the same humor and great characters from the old games are there this will not be a dissapointment but it will remind us why we liked Rare and Banjo in the first place.
How many new Kazooie abilities, Egg types, and animal powers can there really be? This series needs this change and give us an infinite amount of creative input in the main mechanic will make this a (the?) 2008 standout.