As DrRandy said in the comments, cookies are really far from banana bread. It's going to be pretty difficult. I would suggest instead looking for a banana cookie recipe. Even if you don't like the first one you find, you can use it as a starting point or find another, and you'll go through a lot fewer failed batches than you will if you try to start from your banana bread recipe.
If you do start from a banana cookie recipe, the things you'd most likely want to modify:
- adding more chocolate chips - just do it
- adding more chocolate flavor - replace a bit of flour with cocoa powder
- adding more banana flavor - you can try adding additional banana puree and flour to compensate for the water, but it'll make the cookies more cakey and crumbly, less chewy. You can also just use banana extract.
If you do try to convert it into a bona fide cookie recipe, I'm pretty sure you'll discover fairly quickly that the idea doesn't make a lot of sense. In order to make a cookie recipe, you're going to take all the ingredients besides bananas and chocolate and completely change their ratios. To figure out how to do that, you'll use a cookie recipe - so you'll be converting a cookie recipe into a banana cookie. You'll have to reduce the amount of bananas , too, because a cookie can't hold that much liquid. No matter how you get there, all that'll be left of your banana bread recipe is the fact that what you baked contains bananas, chocolate chips, and cocoa powder.
So to try to answer your specific questions:
(how to convert) If I had to guess, I'd say the best starting point might be a chocolate chip cookie recipe that uses melted butter. You could replace half of the butter with bananas and see what happens. From there you could possibly add additional banana and flour, turning it into a cakier cookie with more banana flavor. And to get cocoa powder in, just replace a bit of flour with it. But why not instead start from an existing banana cookie recipe? It'll be much closer to what you want, much less trial and error. And I don't really see any way to think of this as modifying the banana bread recipe; you need a cookie base for your cookies.
(will they be like bread) Well, if you just tried to make cookies using your existing recipe, yes, they'll be like bread. If you use a cookie dough as the basis, they'll be more like cookies.
(temperature and time) No matter what you do, the time will be way shorter (smaller things cook through faster). You probably won't have to adjust the temperature that much, maybe 25 degrees either way depending on the kind of cookie you decide to make.
(is the consistency important) Totally subjective. If you want to make something that's obviously a cookie, well, the consistency is the big difference between a cookie and a quick bread. If you want it to be easier to keep (not crumbly, less moist so it won't mold) then again, that's all about consistency. If all you want is to make something that tastes good, it doesn't matter at all. You can spoon sufficiently thick quick bread/muffin batter onto a baking sheet and bake it, and you'll get basically muffin tops.
