Mail in ballots don’t get rid of secrecy, unless the system has been tampered with, which you could also do with illegal cameras at in-person voting etc. Anonymous envelope-within-envelope is a pretty standard way to keep secrecy, and many states do it, like mine.
Is that really a problem? Since there will be lots of evidence and criminals tend to fuck up quite a bit this should be well documented. Unless you think that those election fraudsters that buy tons of votes from civilians have better opsec than drug dealers and the like.
