Joint limits and mass tuning are the least creative part of a character pipeline. In UE 5.8 the built-in MCP server lets an agent port them from a finished character in minutes. This is the exact recipe, including the one part that stays manual.
https://dev.epicgames.com/community/learning/tutorials/pXjG/unreal-engine-porting-physics-asset-tuning-between-characters-with-the-native-mcp-server-ue-5-8