Have you had an assessment done by an occupational therapist? This is exactly the kind of thing what they are trained to figure out for patients on an individual basis.
When my wife became unable to transfer herself, she had an assistant help her with a gait belt. If you don't have anyone to assist you, you could talk to your health plan about providing a home health aid to help you twice a day, in which case you would have to time your bathroom breaks to coincide with the aide visits. My wife used Oxybutenin to help control her bladder and a Hydrawand to stimulate BMs, so her bathroom visits were always at the times of the aide visits, and she never had to wear a diaper--ever.
When the gait belt became ineffective, my wife was prescribed a rolling, tilting commode chair. We used a lift and sling to transfer her into the chair. The tilting of the chair was very important for properly positioning her on it with the sling, because the sling naturally puts the body into a somewhat reclined position.
Although the commode chair came with a basin, I replaced the basin with a simple plastic splash shield so the chair could be rolled over the toilet, where she did her business just like anyone else. The Hydrawand was fantastic and kept everything clean.
Importantly, the rolling, tilting commode chair had a head/neck support. We used Velcro on the head support to attach a terry cloth headband, which we put around her head when the chair was positioned upright over the toilet. This prevented her from nodding forward. The armrests on the chair prevented her from falling to the side.
We know other PALS from support group who use diapers, so I guess that is okay for some people, but I think our no-diaper system worked pretty well.