I've never needed to reconfigure Oblivion controls but isn't there a section for it in the in-game options?
If not, a script using IsKeyPressed and TapControl functions might work. My doubt with that idea is that TapControl running repetitively while you hold down your new pan key would probably just rapidly change from 1st and 3rd person views... Does anyone know of a function like TapControl which holds the control down until told to release?
Having said that. Does holding R not have the same effect as holding the mouse wheel? When I tap the mouse wheel I switch between 3rd and 1st person, which is the same as tapping R...
Bit of a confused self-narrative but maybe something I'm thinking will help.
Maybe...
~Blessed be