Altering sleeves

I’ve tried this tunic a few times. It didn’t go well; I used some very cheap poor quality rayon I had left over from some Halloween costumes, and I sewed it twice with that, and then I tried it in quilting cotton. The rayon ones obviously are unwearable, but the cotton one turned out okay (I need to add a busy adjustment but otherwise it worked). Problem is, I don’t like the sleeves, specifically how they flip up slightly at the hem (I’ve sewn only the short sleeved tunic). So, I am wondering if it would be possible to alter the pattern to accommodate a regular set in sleeve. I really love the neckline and the front panel detail so I’d love to be able to make this pattern work for me. Any tips for getting started on a big alteration with the sleeves?