@ragucis as suggested by @Kiran_Vedantam maintaining all the content of a site/domain under single content hierarchy is ideal and efficient way of using AEM.
But as you said, you are planning for some transformation/revamping and seems like you are rebuilding your content in new hierarchy. In this case, you can leverage your CDN and dispatcher rewrites to route the incoming request to correct paths based incoming patterns.
At CDN:
If my request is <domain>/a/b/c ---> <dispatcherdomain>/content/branda/a/b/c
If my request is <domain>/a/b/e ---> <dispatcherdomain>/content/brandb/a/b/e
And here dispatcher acts as passthru to publisher
Or
CDN acts as pass thru
At Dispatcher
Use your vhost rewrites todo same as above.