How much would need to be reimplemented? Like is this a problem going back to the entity prototype itself or would it 'only' need transport belts (and presumably their logic) to be remade?

Decided to do some poking around in the api docs, and it seems like the transport belt prototype(s) have their speed set before runtime. Problem is, I would like to change the speed of transport belts while the map is loaded, preferably with circuit signals, and even have multiple different belts ru...