I have not tried this myself yet but you could try L/R pose swap plugin by ky1001 https://hub.virtamate.com/resources/pose-l-r-swap.13649/
Then in timeline make a copy of the animation and use L/R pose swap for each timeline step. Would be easier if all the steps in the animation were in the same line for example- time is at 1 second and has head, chest, hip, hands and feet selected. Hope that makes sense.