There is a designation or certification developed by the NAHB called CAPS or certified aging in place specialist, that a builder can achieve and help design or remodel a bathroom that will be user friendly for the aging homeowner. Some things to consider that may help an elderly person get around the bathroom would be, grab bars and or hand rails in the shower and next to the commode, wider doorways to accommodate a wheel chair or walker, vanities designed to allow a person in a wheelchair to reach the sink and faucet similar to a knee space, and specialty items like walk in tubs with doors on them. There are many other things that can be done but asking a CAPS contractor may be your best bet to achieve the most out of your bathroom.