The tmtest version of Mapview now offers selection to load by region and/or system in the popup that comes up on a generic page load or when you hit the "Jump" button. If you choose at least one region or system, the coords and zoom level will be ignored, and auto-loading of all visible segments is deselected.
I don't think there's a great way to support rte= or cr= through the popup. country= can be done, but looks to require quite a bit more work for what I suspect is little benefit over having to select all regions (use shift to select multiple) or by just reloading the page with country= in the QS params.