[tproxy] MAC and VLAN transparency

I am using tproxy to do source IP address transparency on our proxy, and it is working well. I would like to extend the functionality of tproxy to provide source MAC address and VLAN transparency as well. The proxy in question runs as a transparent bridge, so I think that I have to integrate the tproxy framework with ebtables, but I'm not 100% sure how to go about that. I would like to set up an ebtables (or equivalent) rule that does source MAC natting, similar to the source IP addrses NAT rule used by tproxy today, and I would also like to rewrite the VLAN tag in the outgoing packet to that of the original connection, if any. Can anyone give me any pointers about how to best accomplish what I am trying to do? Thanks, Cam