Wirelessly posted (BlackBerry9630/4.7.1.40 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/105)
You don't really have a chance for an upgrade on CO; they don't give out elite upgrades on BusinessFirst flights which either IAD or EWR-NRT would be.
If you want the 25% RDM bonus you would get for being elite you would need to fly on UA or CO. If you are willing to forgo that ANA is also an option. I don't think it is worth the connection on CO unless you really want to stay on "home" metal for some reason. And I'd bet that ANA will be more comfortable than UA. Of course, later this year you can get free access to E+ on UA which might skew that comfort benefit.