I did plenty of ab work - weights, pilates, etc..- with my loop ileo. However, you MUST make sure your surgeon has cleared you for physical activity. He has to make sure you are healed. Also, your doctors may want you to limit the amount of weight you are lifting overhead, but that surely doesn't stop you from working out or doing other ab work.
Basically I did almost everything I did without an ileo, while I had and now have again an ileo. Have swam, biked, ran half marathons, and more. No need to limit yourself, as long as you have doctors clearances.