Yes....what Garden Whisper said.
"Hardy Chicago"....aka: "BENSONHURST PURPLE" Easily available, and, reasonably priced. Obviously, the less common name, has a Brooklyn connection, and may appeal to your friends, who live in Brooklyn.
I think the limiting factor in this situation is the amount of sun that the tree...any variety of tree...will get. Brooklyn is also probably in climate zone 7a/b, and the "HC" will probably survive NYC winters without protection. It also ripens figs earlier in the season than some of the varieties that you mentioned in your posting. 'HC" can be found/bought, usually, FMV-free!
I'm sure some other varieties will work, but at least "HC" will give them some of the best tasting, dark, figs that can be grown.
Good luck. Nice idea for a appreciation gift. Literally, a gift that keeps on giving.
Frank
EDIT: Try mentioning to your friends that the fig tree growing in their backyard will probably need top-dressing with granular limestone, needs fertilizing, and they should try pinching out the terminal buds to induce earlier fruiting. Perhaps the poor fruiting characteristics that they are experiencing with their grounded tree, is due to neglected cultural practices.