The best remain to do it with the Unreal Engine 3 or Cryengine 3.
Both are available for Free and there are damn easy when it comes to export or work with 3rd party tools.
AVP2010 probably won't have any SDK and I doubt it's a very accessible engine since Rebellion made it so they may use very specific tool that people don't know how to use.
At least I know I can work with Maya easily and then import to unreal and Cryengine. They both have plugin for it.
Anyway, we're a bit off topic. PLEXI made a topic a year ago in the Fan section concerning the game but this attempt failed due to the lack of time and the fact there weren't any coder.
Start it once again now would be unwise I think. We need to be sure to have everyone on the board and ready.