I like your acknowledgement of pure political tactics by then.      I started laughing at the 'arguments' against people voting by mail.  Something about the opportunity for voters to receive vital informormation about the issues from the candidate last minute exchange!!!   a) it's funny to think that anybody cares about the 'arguments' at that point. b)  It's just 3 more weeks of misinformation and any serious discussion of issues is long over.  

Besides you can hang onto you ballot for a longer period of time if you want to anyway.     I'd guess 60% or more of voters will know their candidate at the end of the primary anyway.   If they aren't paying attention until the last 3 weeks then they are probably not mail the ballot in.

Here's an idea shorten the entire election season about two months and save some money.   Go  to ranked voting with an open ballot and do it all in one election.  Enfranchise minor party's in the process, which is also why the 2 major parties will fight it.