Most of this is actually unnecessary. `RouterWorkerHelper` proxies everything you need from `MessageHelper` (so you can just replace the `self.msg_helper` with `self.router_helper` everywhere) and all the persistence config is already handled by `get_router_worker()`. (We do *something* with `worker_name` in there as well, but I don't recall what offhand.) Basically all you need here is the `add_helper()` for `RouterWorkerHelper` and `self.router_worker = yield self.router_helper.get_router_worker({})`.

The helpers really need to be better documented, but I haven't had time to work on #824 yet.