It's worse than that. BA goes from MCO to LGW, not LHR. You'd have to schlep across London (with bags) in order to get to FRA.
Either DFW or ORD are probably better choices. If via ORD you might get lucky and get a 767 with new business class seating; if via DFW it will be on a 777 with old-style (but still comfortable enough) J seats.