Do you want to use these as middles? Or first names? Or both?
I guess it depends on how the name feels to me. I would def love to find middles, but if I found something that really struck me I would use it as a fn!
Do you like any of the names as-is? I don't have a feel for your taste yet.
Some of the obvious variations...
Jean - Gene, Eugenia, Eugenie, Jeanne, John and variations like Sean, Ian, Johanna, Jane
Mary - Rosemary, Mariel, Marian, Marybeth or Mary-Jane (Mary-Jane could technically over Jean as well)
Christina - Christopher, Christian, Christiana, Christabel, Christine, Kristen, Kirsten, Christa
Beatrice - Beatrix, or Bea is a cute one-syllable middle I've seen
Laura - Laurel, Lauren, Laure (Marie-Laure)
Frank - Frances, Francine, Francesca
Irene and Isaac I'm stumped on, other than Irena and Ike.
I like the name Franklin as derived from Frank
Franklin Isaac or Isaac Franklin has a nice ring to it.
Lorelei derived from Laura. As in Lorelei Christine or Lorelei Marie.
You can also do Beatrix instead of Beatrice. I love the name Beatrice but if you're looking to make it a MN i would probably pair it with another classic name.
or you can shorten it to Bea