Well, you KNOW this thread is going to excite me! 
I live in zone 7, too, so we’re both right on the edge of what bananas can handle. That makes our climates perfect for landracing them for cold adaptability.
Here are some thoughts you might consider.
Musa basjoo: I’ve been told that it’s seedless, and no one has ever been able to get it to make seeds. This, obviously, bums me out extremely. This, obviously, would not stop me from trying to cross it with anything and everything else that flowers at the same time as it.
Musella lasiocarpa: I know very little about this one, except that it’s highly cold hardy and weird. It’s in its own genus! I’ve been told it doesn’t make fruit, but it looks like it does have banana-shaped fruit in a stock photo I found, so it may be possible to get it to do something cool. It may be worth growing and trying to cross with everything else. I’ve been told that some experts are considering moving it to the Ensete genus, so that implies it’s more closely related to the Ensetes than the Musas. If you want to breed with it, maybe try growing it alongside Ensetes.
Helen’s Hybrid: I want that one so badly! (I’ve never seen it called “Musa helens,” but that doesn’t mean there aren’t people who do that.)
Musa chini champa: BOY, do I want that one, too. I haven’t been able to find any seeds. It seems to be rare.
Dhursay: This is usually called Monthan. It’s on my list, too.
Blue Java: Also known as Ice Cream. This one is particularly interesting because it’s the most fertile of the seedless bananas. Apparently if it’s pollinated, it’s often quite happy to make a few seeds. That makes it a really good prospect for breeding.
Musa sikkimensis: This is on my list, too!
Here, have a long list of things I’m keeping my eye out for! 
Bananas suitable for zones 7a-9a
(arranged approximately from most cold hardy to least)
Seedless – all Musa acuminata or acuminata / balbisiana hybrids:
California Gold banana
Dwarf Orinoco banana
Dwarf Namwah banana
Blue Java (Ice Cream) banana
Misi Luki banana (a.k.a. Mysore / Pisang Ceylon / Pisang Keling)
Raja Puri banana
Grand Nain banana
Dwarf Brazilian banana
Praying Hands banana
Monthan banana
Ae Ae banana
Seeded wild species, Eumusa group:
Musa basjoo (This one is hardy to zone 5! Unfortunately, it seems to be seedless.)
Musa sikkimensis
Musa thomsonii
Musa yunnanensis
Helen’s Hybrid
Musa cheesmanii
Musa balbisana
Musa velutina
Musa ochracea
Musa chini champa
Musa aurantiaca
Musa rubinea
Musa flaviflora
Musa violacea
Musa ornata
Musa laterita
Musa anestor
Seeded wild species, Callimusa group:
Musa johnsii
Musa haekkinenii
Musa beccarii
Musa campestris
Musa hirta
Musa coccinea
From what I’ve read, all the species in the Eumusa group can cross, and all the species in the Callimusa group can cross. It doesn’t seem to be possible to cross outside those groups.
Those are all in the Musa genus. Eumusa and Callimusa are subgenera.
There is also the Ensete genus, which is its own thing. I don’t know very much about them. They’re said to not make bananas, but they sure do have bananas on them in the pictures . . . so my guess would be that they do make bananas, but the bananas don’t taste very good. If so, those could be bred for improvement!
I know little about Musella lasiocarpa except that it exists and it looks really cool.