Bandwidthd on multiple interfaces $100USD
bandwidthd itself can only listen on one interface at a time - this is baked in to the C code.
Option 1 would be to patch it and have the patch accepted into ports, then update the pfsense bandwidthd menus accordingly and have that accepted in to pfSense
Option 2, update the pfsense package (menus etc) such that bandwidthd runs separately for each interface it listens on. This would have the side effect of requiring the reports page to have more tabs, service watchdog to have several entries (similar to VPNs), etc, which is included in the bounty. All this accepted in to pfsense.
$150 USD upon completion.
Option 1 is probably less coding (maybe) if you're careful in the C code (or can find someone elses patch) and most minimal in php. Probably this is the "correct" approach.
Option 2 is all pfsense and perhaps the path of least resistance. Having seperate reports might even be seen as a feature.