Cool pic and awesome idea! Connie would make an interesting addition to Lilo's ohana. I'm surprised I haven't seen this crossover before. I think Connie would make a more laid-back, understanding, and active big sister than Nani. If both the Crystal Gems and the experiments exist in the same universe when it's possible Jumba created the Experiments in order to fight against the Diamond Authority on the behalf of the U.G.F.
Heck, it's possible that Steven works alongside Lilo & Stitch in order to rehabilitate the experiments. While Jumba tries to cure gem corruption out of scientific curiosity and to better appreciate this very evil "song". Pearl and Pleakley would probably get along just fine. Amethyst would make an interesting role model for Lilo, she and Sadie could watch horror movies together. A fight between Garnet and Stitch would be something to see. Gantu and Jasper would probably work together quite well, and Peridot could probably provide him with some kind of strength enhancement. And if there's anyone who could make Angel an interesting character it would probably be Rebecca Sugar. Someone should really make that fanfic soon!
Cool pic and awesome idea! Connie would make an interesting addition to Lilo's ohana. I'm surprised