I don't think I've ever seen the equivalent of the 6 week bran muffin recipe for banana muffins.

(These days most experts recommend against the 6 week bran muffin recipe because it can grow bacteria in the refrigerator.)

That having been said, I think the biggest challenge would be the bananas, I think they would start to turn a bit funky. It might be possible to mix up everything except the bananas and just add them in when you want to make a batch of banana muffins. The nuts might soften up over time, too.

Banana muffins freeze very well, before I went on the keto diet I was making as many as 120 mini-muffins at a time and freezing them in small bags of 2 or 3. My wife would grab a bag out of the freezer, stick it in her lunch bag and have them during the day. (They're pretty good if they're still a bit frozen, too.)

I haven't found a good recipe for keto banana muffins, bananas are not a low-carb food. I did find one that used banana extract, but we didn't like them. I might try it again some time using less of the extract, so that it has just a hint of banana flavor, not BANANA!!! (Putting in only a small amount of banana might work, too.)

I've been playing around with recipes for keto-friendly blueberry muffins. (3 or 4 blueberries in a mini-muffin only add about 5 carbs.) They seem to freeze well, too.