There is too much personal preference, disparities in physical size and abilities, and variations in home designs and layouts to have anything fairly simple and straightforward evolve to promulgate what we would like to achieve.
Therefore, as aging-in-place professionals we need to focus on one home at a time and educate people on what is good practice while being an advocate of what should be happening and why. There does not need to be any requirements to meet or measure - just common sense and an intuitive interpretation of what can be.
We would love to see people incorporate visitability strategies into the exterior of their homes. We would like to see an 18"-24" approach or access area next to where someone opens the front door or has it opened for them (from the inside). We would want to see a substantial standing and approach area near that entry door that would allow someone to stand in that 19-24" approach zone without fear of being in the way of the opening door. We would like to see a significant covered porch or entry that would protect both occupants and visitors from inclement weather while they waited for the entry door to open and then entered the home.
While laws could be passed to mandate each of these ideas, that would be the wrong course to take. There simply are too many variations in building designs and styles to make one law applicable to every situation. Therefore, we need to educate people on what is desirable for them to have - for their own good and well-being as well as the safety of anyone who calls upon them (invited or not).
We would really like to see covered porches that afford total protection from precipitation, but some homes don't have the room to install one or their architecture doesn't lend itself to such a concept. Lower, larger windows would be a great idea. Wider hallways and doorways are very important, but requiring them versus conveying to people why they should have them and why it is desirable to have them is a better tactic.
There are many people who just don't have the financial or planning resources to accomplish good design so they will continue to live as they have been or will make one or two smaller improvements as their needs dictate over time. Perhaps we can identify some funding sources or interest more civic groups and agencies in the need for such programs and get them behind such an initiative.
The key is getting people to want to make the universal design improvements that will help them and make their lives easier because they recognize that these will contribute to their own safety, comfort, convenience, and accessibility. Then we can locate funding sources and some possible incentives to help them. Private desire and activity is going to carry the day rather than a public insistence on what needs to be done.