alternative controller design

Another option would be to autoload only the controller file that matches the first word in the URI. This could be done in run() directly before the call to route_find(), so that dispatch* functions could be placed in the controller files.

Both these options would make controllers more re-usable, and load fewer files per request.

About loading the controller file that matches only the first word in URI, it can be done by defining your own autoload_controller function.

function autoload_controller($callback)
{
  $uri = request_uri();
  // ... find first word in uri
  // then load the matching controller
}

I like the idea you illustrate before, some kind of default routes for a resource. But I think this should be left optionnal, keeping Limonade more versatile and not as opiniated.
Perhaps by defining a user definable function default_routes called in route_find if no route found:

function default_routes($method, $path)
{
  // try checking a controller file foo.php...
  // return false or a route array...
}