I think the real question is just the batteries. Electric motors aren't new, the technology has been around for almost 130 years. The only problem is that you need a set of wires following you around to provide power. . . .
Source : Pullmans 8535, 8514 and 8537 at the North Cambridge car house on October 10, 1967
They were quiet, didn't pollute from the tailpipe (yes, there are still emissions from the power plant), and they handled pretty well. With a single electric motor,maintenance was pretty simple. Plus, there's no combustion engine - so no oil changes. If you can design regenerative braking system, that saves on brakes too. Electric heat is a no-brainer.
All of those things should still be true today, we just need to build a battery system that can power them. A school bus is a good candidate for an all-electric - you've got a known route distance, plus a safety factor, so you know how big of a battery you should need. You've also got a solid 8 hours for the bus to sit and charge all night between runs. (While it might not take 8 hours to charge an individual bus, if you need to charge a fleet of 20 buses, and you have enough power to charge 5 at a time. . .)
I think the real issue is how well the batteries hold up. How many charge-discharge cycles can they take, and how much will capacity degrade over time? The electric drivetrain works and ages decently with smaller vehicles - as hybrids with the Prius, and as all-electric with the Tesla, Bolt, etc.
Maybe it's possible that wheel-based motors will allow all-wheel-drive models in the future.