Warning - a very computer technical post.
I took some time, but I have finally chosen the solution to handle my thousands of photographs. Unfortunately keeping track of thousands of photographs has become more or less impossible, and after testing several photo management software solutions, the choice has fallen on Digikam.
I also considered letting Lightroom be my primary photo vault, but I did not feel comfortable having a propitiatory format handle that amount of information. Digikam is open source, where the database holding all my information is easily available. Basically Digikam does not own my data through a lock-in effect. Another great advantage is that you can set it up to use a MySQL database instead of the default SQLite database. This makes using Digikam across several computers on a network much easier, and was one of my primary reasons for choosing Digikam.
I still use Lightroom for the much of my post processing, and I am using my computer science background to develop a Lua plugin for Lightroom, that will allow Lightroom access to my collection in Digikam. But it will take some time before that is done. When that is done, I should have a complete solution. But when I finally have completed the solution described here, I will probably have some new requirements that need solving. So I am guessing this is a problem that is never completely solved.