I now have both my legally purchased  ToA licenses running. One is 2.02, the other is 2.04. When logging in in 2.02 (probably 2.03 as well), I can select different accounts. In 2.04 I am automatically logged in as the user of record for the v2.04 installation.

so

If you have purchased multiple licenses for the purpose of maintaining  more than three MV characters, you will not be able to use them all if you have a single installation of 2.04.

I will now bravely proceed with an attempt to complete a 2.04 MV game and see if I still get the catastrophic  game freezes that plagued me with v 2.03.