Hey Eric!
I've eaten a vegan diet for about 4 years while having an ostomy and I definitely remember having some changes in my output initially, but it is hard to say what that was caused by (better hydration, more fiber, less constipation from meat and diary products). If the output is just more liquidy, it doesn't necessarily have to be cause for concern. I have also probably had more gas since switching to a plant-based diet, but I honestly think it is normal. I think the important thing is that you feel hydrated and don't have belly pain from diarrhea or gas. As for the type of pouch, I have never used the closed-end pouches because my output has always been pretty liquidy due to the medications I take. You could always call one of the supply companies and ask to sample a couple of the open-end bags just to see how it goes for a week or so.
Anyways, the plant-based diet has been really good for me, and I think its a great thing to try, even for folks with ileostomies because there are PLENTY of ways to eat plants that don't lead to a blockage. Meat, dairy, and eggs are pretty hard on the GI system, but plants are great in whatever form you want to eat them...pasta, potatoes, steamed veggies...there's an abundance of options!
