I made that function, and Metallissimus helped me a lot with insightful suggestions and bug reports.
The selection in any album is working good now, it allows to send a mail with that list of photos and any form field you need.
Interface in the panel for that? OMFG! That would mean almost rethink all of X3 to work with a database. I see no practical way to do that otherwise. And finally I came to love my X3 without a database. I had to code the few things I really needed, and they definitely didn't need a database. I hope X3 stays that way.