did you already think use Blender serializer from gamekit http://code.google.com/p/gamekit/  instead of implement a new exporter?

Serializer allow bring large complex scenes to Maratis editor for aditional customization or load direct on player.

thanks

I never tested with NLA, I don't now if it works, normally it should,
but for your problem, it's maybe because you are animating objects directly.

There is no support for object animation in the current python script, you need to have an Armature, if you want to animate one object, just create an armature with one root bone.

Can you post a little tutorial export animation?
Can we use the NLA or not?

Thank!