Theres also the Izotope insight. When the team i was working with last year completed the mixdown we were in a very similar position. No middleware and using proprietary software. We worked with a pro mix engineer from the feature film world and they used this plug in with the output of the game routed back into pro tools. I also set up a record function in the pro tools session so we could record, playback and isolate each speaker in the 7.1 mix which was our chosen format. We even ended up using this in review sessions to capture all the action and scrutinise further.
Thats the difficulty with games, theres no linear timeline so when problems occur its harder to recreate and debug the mix. This way, recording all outputs back into pro tools gave us a system where we could get some of these benefits back. Whilst also facilitating loudness monitoring.
http://www.izotope.com/products/audio/insight/
I've since gone on to mix a couple of shorts using this plug in. The pre sets are really helpful. I would definitely join the ranks of engineers recommending this unit.
