I'm honestly not convinced voting machines are a good idea, especially proprietary ones. You are asking everyone to blindly trust the intentions of the company making them. You also risk bugs and hacks.
Public elections need to be transparent, and easy to oversee, voting machines makes that much harder.
One problem that remains even with your theoretical machine is that non technical people are left behind in the verification process. It can be argued that a voting and verification method that is opaque to quite a significant part of the population is undemocratic.