That could have worked.
How does that help secure John Ross' inheritance? It's at cross purposes with your original idea for her being there. I consider the storyline with J.R. in the sanitarium to be, along with Haleyville, one of the two lowest points of the series.
I watched some of season 13 recently, and Sue Ellen still hadn't taken accountability for her actions which led to her being committed to a sanitarium. She was drinking alcohol while pregnant with John Ross, and drinking heavily. J.R. and the rest of the family tried everything else they could to get her to stop for he sake of her unborn baby but she refused. They didn't know as much back then as they do know about the effects of alcohol on a fetus, but they knew enough to know that it was terrible for the health of the unborn baby. Drinking alcohol, especially in those amounts, can lead to mental retardation and other defects. It's amazing to me that even after she got sober she never showed any gratitude to J.R. and the rest of the family for their support in having her put in the sanitarium, protecting the health of her unborn baby.