Crosslinks
Going through a commsat at L1 might not gain you much. After I wrote the earlier post, I thought about using a laser downlink system to satellites in geosynch. The lunar orbiter would beam the data via laser to satellites in GEO (a secondary package on TDRSS satellites could do the trick). The satellites would then beam the data to ground stations.
I don't think even TDRSS satellites have anything like gigabit bandwidth, but perhaps it'd be possible to expand the downlink bandwidth using technology like that on DirectTV. The military has adapted this technology to create the high bandwidth Global Broadcast System payload on UFO commsats.