we love rmunify here and have multiple systems federated with rmunify including office365, google apps, roombookingsystem, showmyhomework, cc4anywhere, activelearn and others.
once a user is created on sims then automatically they are created a rmunify account then automatically they are created a gsuite account for single sign on.
we also have rmunify set for sso auto login when they login to windows or chrome so seamless login for them just click onto gmail and it works.
i know rmunify is a bit of one glove fit solution and you have to conform to their methods without much flexibility and they usually have different support options for MAT because of this but regardless i would federate it and then force everyone to use the new method. if they complain that now they have to go via rmunify to login then you just have to add other sso services to rmunify to make it worth their while. also you can play the 2fa additional security card because rmunify now supports 2fa for apps such as gmail and o365 so that is a bonus.