"Maybe improving FBX would be a better tactic"

Please. With honourable exception of a very, very few, fully IK rigs, my PPro_11.3 breaks FBX imports after v6.1. We're up to v7.5 ?? Blender etc I/O plug-ins seem to generate three varieties of rig, and PPro_11 will only grok one correctly. Yes, the rarest, 'trad' type. Else rig loses its root, and import variously fails between Oopsie and Splat...

But, given those few exceptions, I must hope that Poser will become fully compatible with MakeHuman and other FBX figures...