What upgrades are needed to handle a Twincharger?

Well, they really don't, that's what supercharges are basically made for, to have the same purpose as a turbo, but prevent turbo lag..
I honestly don't see what the problems you would have with it. Compound/Twin chargers are extremely practical and reliable if tuned and configured correctly.

 

Wasn Lancia the first to employ a compound charging system on a manufactured vehicle?

 

Centrifugal superchargers don't prevent lag, they have step up gearing and provide little to no power down low. Now a positive displacement supercharger does provide low end power. They being belt driven doesn't mean that a centrifugal supercharger has a linear power delivery.

 

Do a sequential twin turbo setup after building the motor, tranny, ect and be done with it.... Better than anything I have read mentioned so far.....