Could you add compatibility for "Factorio Plus Plus" please ?
https://mods.factorio.com/mod/fpp

Done?

FPP has some extra belts
fast-express-transport-belt
superior-transport-belt
fast-superior-transport-belt
highspeed-transport-belt

I guess if you wanted to make this mod universal, you could
- grab all logistic enties defined in the "data-final-fixes" stage
- workout using "next_upgrade" what the original starting belt (it would be a logistics entity that was not referenced by any "next_upgrade" atribute)
- then walk forwards using "next_upgrade" and double the speed

Yea, the new version (0.3.0) makes it all automatically, but based on the standard belt speed.
So if without mod speeds are 15, 30, 45, 60, 75 etc., then they are tiers 1, 2, 3, 4, 5 and new speed will be calculated as 15, 30, 60, 120, 240.