I had j pouch at age 24, had baby at age 39, was breech, and I fought for vaginal delivery to avoid more scar tissue (all my docs said shouldn't be a problem, and that scar tissue was some of the strongest tissue, so not to worry about tearing/ ruining pouch). It all went great. BUT... If I have a second kid I don't know if I would try and do vaginal or c-section. My new surgeon highly recommends c-section, but he also thinks all women should have c-sections, ha! I have had numerous conversations with the specialist at Cedar Sinai in Los Angeles where I live and they are some of the MOST informed people about this. They say so much of it comes down to personal opinion, particular cases, and doctors. But they have said either choice is usually on the table. I personally am thrilled i did not have to have a c-section, because my recovery was very fast and pretty easy. I had a blockage the day after delivering, but that was because I ate a stupid complex sandwhich and should have been on smushy foods for a while during post-partum as your guts are all sort of moving back into place. It resolved within a day and was ok. I am not sure a c-section would have made a difference to that.
But three years later I had to have j-pouch tweaked because of a stricture that had probably been there for years, but finally found. I also had a fistula they fixed at same time. I was like you; very hard iliostomy experience (both first time and second time just now), couldn't gain weight, depressed with it, leaking problems etc. But now I am 3 weeks post take down and doing great! I am much older than you, but we still have 9 frozen embryos, and trying to decide what to do with them. (yes had much difficulty with fertility, because of scar tissue: my fallopian tubes don't seem to meet my ovaries properly).
If you are opting for a c-section, make sure you have a GI doc on-hand that is familiar with your anatomy. A friend who had twins who also had a j-pouch had a problem where because of scar tissue when they took out the uterus it had adheared to her bladder and tore it a bit, so there were complications from that. Its SO HARD to make these decisions! good luck.