You’re probably getting a bit bored of this, but cycle.travel does too (in fact it spits out a couple of warnings about circular relation references every time I run OSRM…).
But for my purposes moving to type=route would make things simpler. type=superroute doesn’t add any value.
(I like the idea upthread of grouping spurs and alternate routes in a route_master relation, as long as the component relations are appropriately tagged without having to refer upwards.)