You cannot create a campaign with Conversion Optimizer bidding scheme, as you said it must become eligible first. I interpret this RMF requirement to mean you must support converting from another bidding scheme to Conversion Optimizer once a campaign becomes eligible. The best explanation of how this is to be done is this post here :
You should check with the policy team to confirm that the above assumption is correct before proceeding, but it is really the only way I can make sense of it. However, I do not work for Google and cannot confirm this myself.
Hope this helps.
Jason