Your company is engaging in a new platform, treat it that way. When planning your implementation, plan according to business – not the existing SharePoint structure. The business first approach is critical, new functionality and tools like MS Teams will change the way your users engage with SharePoint and many of the features you had on-premises will no longer be available. Trying to replicate your existing SharePoint sites could be time consuming, expensive and will have a negative impact in the long-term adoption of the new platform. There are still scenarios that warrant leveraging old SharePoint sites, but use these sparingly. Rather focus on understanding what your users need and build according to that.