Thanks a lot. I developed and support a standalone desktop application which contains customer-specific tiled maps, and it can get unwieldy.

A pivot at some point to these types of archives is an option, but I'd like to roll forward existing customers as well.

If you have access to SQLite in your desktop application then there isn't any big wins from using PMTiles over MBTiles; PMTiles does have some special design around tile-deduplication but this is possible in MBTiles too by using table views.