Surron 2-speed gearbox - does it worth ?

I'm toying with the idea of making a two-speed transmission for surron
I would give the transmission between belt and chain drive - instead of the connecting shaft that has one side sprocket and on the other side belt wheel.

First gear will be for offroading - probably same ratio or slower than classic surron power train ratio for more torque and less speed like 58t sprocket.
Second gear will be for street riding - higher top speed without Field Weaking - better for motor and efficiency.
Probably it will have also neutral between gears - bike can be pushed easily, lower losses when descending a hill.

Gear wheels will have sync rings - rider will must shift at zero load on gearbox - will not have a clutch.
Advantage is surrons with stock controller can do higher speed on road without losing offroad torque.
When you change chain ratio to 58 sprocket on wheel you have only torque and loss speed, gearbox can use both advantages.

What do you thing about it, ist a dumb idea ?

great idea.. would love to see it executed.. have you seen DOB D1 etrial ??

ref:
https://endless-sphere.com/forums/search.php?keywords=Dob&terms=all&author=&sc=1&sf=all&sr=posts&sd=d&st=0&t=0&submit=Search

Could you use an existing bicycle 3 speed IGH if you were specifically shifting when off the power? Not sure how long they would last.. Im guessing some kind of adapter would need to be made to attach the drive gear.