I'm not sure a direct drive is possible with EV conversions. You still need to match effective RPM range with diffs. And replacing transmission with a simpler specialized diff would cost much, much more than just using the existing transmission in place.

Negligible. Roll the windows up if you want that range back.

I still think it's dumb and they should package it to replace the transmission and stuff all the batteries where the engine would go.

It would be "easy" to make the motor replace the bellhousing and midsection of a 4L80 and then simply provide the same output so you can stick whatever tailhousing you want on it. Put shifter on the side in the same spot, etc, etc. Could've packaged the batteries to fit in the same place as a SBC longblock.

I can't really come up with a "good" reason they did it the way they did. Like either replace the engine so it can work with "any" transmission that can handle the torque (i.e. most of them) or replace the transmission too. Don't replace the engine and then mandate a particular trans. The only reason I can see to do that is if it's some sort of wink and nod deal where they know that it's easy to make it work with other transmissions but they're not touting it as compatible to cover their asses.