Need the ability to group content in the CMS for Spire with more control over URL structure

We have over 600 pages of content that we are migrating over from Classic into Spire. We have specific URL's for those content items that we need to keep intact. We also need to be able to "group" that content without impacting the URL structure of the content (much like what you can do in Classic). Our concern with placing all that content on the root aside from any performance degradations is the significant maintenance challenge it will create with updating all the linked pages to point to the new URL structure. Not having the ability to control our URL structure will also negatively impact our SEO as well. If there was a way to provide a setting in the CMS to either use the folder structure or specify the URL at the node level would be ideal.