If you'll be checking in originally for a BE segment, you should expect to pay normal BE checked bag fees. Note that combining the tickets would be bad, as the most restrictive (in this case, BE) fare rules would apply to the entire itinerary. If it's a domestic BE connection to an international main cabin segment, for the combined ticket (in principle, since tickets cannot be combined), the $199 change fee would apply rather than the $99 fee to change a domestic BE ticket. This is just a hypothetical thought experiment since tickets (and/or PNRs) cannot be combined.