Yes, this seems like the ideal solution. A bus is big enough to where you can easily engineer a quick attach/detach "cartridge". Since it's all operated by the city (or private entity), you also don't have the issue you would with consumers where you need to worry about users turning in damaged batteries for good ones.

The battery will still be ridiculously heavy and very large, well outside the limits of human ability to move it. So you need some sort of machinery to do it, as well as a human operator.

Also, keep in mind you don't just need very robust electrical quick-connects, you also need fluid quick-connects for the heating/cooling. As well as a system to bleed air from the loops inside the bus.

Some back of the envelope math:

Let's say the bus needs 50 miles of range, and it runs at 2 kWH per mile, so it needs a 100 kWH battery. Assuming 200Wh/kg density, the battery will be at minimum 500kg.

Lots of EV cars have batteries that big.

Yes, and it’s a structural member of the car that can’t be easily swapped out.