Actually found solution (using Maya) after almost one day!
- Export UE4 Mannequin Skeletal mesh as fbx
- Open Mannequin in maya
- Import your model into the same scene
- Fit your model to Mannequin skeleton if needed (DO NOT TOUCH JOINTS)
- Substitute Mannequin geometry with your model geometry
- Unparent your model geometry and Mannequin joints
- Export as fbx
- Import into UE4 choosing Mannequin skeleton as default
That is it! Animations should work smoothly. If smth looks ugly you always can repaint weights in Maya and try again. Good luck!