The way cycle.travel works under the hood doesn’t really lend itself to lots of options I’m afraid – essentially each new option means renting an additional server (and servers are expensive!). As cycle.travel’s focus is quiet and traffic-free routes, I don’t have any plans to add a fast road option – sorry.

You might like to have a look at brouter, which is a very customisable route-planner and has both “Fast bike” and “Shortest” route options.