Glad you didn't get hurt any worse. You had to hit HARD to break your femur. Holy Hell.
We had a platform with a pop up and used a regular 6ft step ladder as the ladder (good angle). One trip up I watched my dad open the popup and get in from the ladder and I build a landing platform before we came back up and attached that to the platform. After doing it I was dumb for not having it in the first place.
If you want a 4x4 platform, build it 6x4 and use the extra 2x4 as a landing area. Even a 2x2 landing area is enough. Only cost an extra $20-30 if you build it out of 2x8's w/ 2x4 rails.