In Minnesota, the problem of individual untrustworthiness is handled by putting multiple people on every task - and those people must be from different political parties. So any time ballots are handled, marked or unmarked, members of at least two different parties are present.

So simple, so effective.

That's how it works in the 9 states I've lived in personally.

Translate that concern into action. Volunteer to be an election official yourself and keep an eye on everyone else. Participate in how this thing works. It's really rewarding.