Jaime, I'm not an expert, but I'll wager an opinion.

I would not recomend that. If they are too and skinny, and it's not normal for that particular type of banana, I'd be afraid that cutting leaves would actually hurt the growth.

I think the leaves would grow back, but the leaves that are there now are inportant in collecting sun for the plant.

If you want to bulk them up, I might suggest making sure they are well fed, properly watered and have enough sun. Banana's like all kinds of fertilizer, and plenty of it. You can feed them practically anything you have.

Either way,,, Good luck!