When I import a character from fbx file with other units system I use the "Convert Units" checkbox option, on the "fbxcharacterimport" sop to put it at real size. Then I can do all manipulations I want and go to save it with animations as "agentdefinitioncache".
BUT
When I import this agent it was back to wrong scaling as if I disable "Convert Units" at first step. If I directly import fbx from agent sop scaling is good. But how can I well export my character to agent definition cache with right scaling on load ?
You should wire third output (animation skeleton) into the Agent from Rig SOP, not the second output (bind pose). The bind skeleton doesn't necessarily have all of the joints Because of this, when the animation clip is applied some of the local transforms are lost since they aren't joints in the agent's skeleton. If you turned on Set Current Clip on the Agent Clip SOP you'd see the same issue as when the agent definition is loaded onto a new agent instance.