Implementing ToMVC

Wouldn’t it be problematic to instantiate the Request object before anything else? I imagine the Request would hold GET, POST, SERVER, SESSION, etc. data while they will not be needed for every request. For example, I would initialize session only for some pages and I might also want to have two separate sessions for different pages/requests. I imagine the Request object should be initialized by the router because before we know which M/V/C to call we don’t know what request data is needed?