I would totally pay extra for this feature. For context to Waze folks reading this, there is a strong lack of good motorcycle options on Android - especially if you also want Android Auto support. I realize motorcyclists are a small percentage of your users, but there's a market segment here ripe for the capture :)

I can't afford a motorcycle specific Garmin XT Zumo right now; a fellow rider said he has access to curvy road map on Waze. i just can't find it....

That is a great suggestion that is very close to my greatest wish for now.
I would love the option of driving on slower roads. Think of it as an extension of "avoid highways" but with the option of setting the speed limit that you don't want to exceed.
I would love to be able to set Waze to calculate routes never exceeding the speed of my choice. Especially when we decide to drive slowly through the landscape in the cabriolet. When you drive with the top of you want slower roads than usual because it's a lot more comfortable.
I guess the same thing goes for RVs, camper vans and trailers that prefers a slower than usual speed.
Sometimes you WANT to go slow and enjoy the scenery instead of racing from point A to point B. Sometimes I do.

Waze, please get inspired by Calimoto (https://calimoto.com/en/motorcycle-trip-planner), which really finetuned the navigation for motorcyclists. However, their maps rely on OSM which means that temporary road closures etc. are not reflected. Waze can easily leapfrog Calimoto if only navigation could yous slightly different setting in the algorithm and if motorcycle mode would be transformed to a profile (changing various app settings at once) rather than a one of many app settings with no relation to other settings.

I would pay for a curvy road option on Waze