Making combo boxes more keyboard friendly

Combo boxes in Gnome are difficult to navigate by keyboard.  There's a
simple bug report about it here:

https://bugzilla.gnome.org/show_bug.cgi?id=643853

I've always found this issue a minor inconvenience, but for blind
users using Orca, it's a much bigger deal, since they cannot grab the
scroll bar on a combo box and quickly find the item they want, and
instead have to arrow down through the whole list.

Is there any chance keyboard navigation of combo boxes could be improved?

Thanks,
Bill