Installing a hand hold and a step?

I purchased my handles from Vern several years ago. The came with everything needed to Install, bolts, nuts, everything. Works great and I was able to quit using stool and rope. Ken Crofut N87207 

I like your stirrup idea alot.

Welcome to the "club"! We think alike. I came up with the step stool and rope too. Don't need the handle as I can reach cockpit which is always open in my hangar - keep a blanket over windshield and cockpit to keep clean. My hangar is somewhat away from the main stream and I always return to same airport. However, I think most airport folks would just smile and think what a novel idea and respect that we senior citizens are still flying (76 years after solo). If they do, "act like a nut", and are verbal, I would just respond, "  flying keeps me young and you should hope that you can still be flying when you reach my age"! FWIW
Haven't thought of a way to attach a step with the required strength and then there's the FAA, and your IA! Then again, after installing the handle, fabricate a rope/strap with hook to clip into the new handle and extend down to almost the trailing edge of the wing and thus becoming a "Y" shape so it would always be oriented parallel to the wing trailing edge terminated with stirrup, like on a horse saddle, that one puts a foot in to assist up. Quickly remove and . put in baggage - don't need on return and leave laying on wing if in a hangar or keep in your car. No FAA involved! Second thought, use metal cable covered with plastic tubing as fabricated DIY or have mechanic fabricate.
Someone sells the handles in the club - might check with Vern FWIW

I would like to add a handhold and possibly a step to my Ercoupe in order to make climbing in a little easier for me and my old bones. Is this possible? Is it advisable? What should be considered?
People act like I'm a nut when I use a plastic step with a rope attached to get up on the wing. I would like a permanent step if it is possible.