I'm a little late to this idea. But.
I like the options said above.
I think that in terms of weight a normal bicycle would be at 6 when fully assembled. 3 for the frame, 1 for each tire, and 1 in total for all the random gears and breaks. having light, normal and heavy frames. light weighs less and can go faster but isn't very durable so having too much weight or hitting too many things will break it. normal will be able to hold a normal player with a full inv and maybe a bit more before it starts to get strained and is not going to break from hitting something unless you go fast. heavy being extremely durable and can a lot of weight on it and hit quite a few things without breaking but would be slower. have accessories like bike racks and baskets/bags for them. have it so back racks can have either containers that are made for bikes on them or have bags you put on them. be able to hood flashlights and small hand mirrors to them.
possible add small motors onto them as well (which could be a foundation for motorcycles).