Do you guys really loose that much wort due to hop additions? My double IPA uses almost a pound of hops before the dry hop, and I still go from 7 gallons to 5.5 gallons after a 75 minute boil. The loss I see is mostly all evaporation during the boil.
As far as steaming the hops, I think it might be hard to get the alpha acids from them, and the beta acids derived would dissipate with the steam. If you are worried about volume loss I'd try a hop back or a hop addition at flame out prior to recirculating.