I've been working on this system for a while now, and it's up on the site at last! Now activities can be linked together if one has inspired another. As I write this, there's only a small handful, but you can check out an indexed list of all of the links here.
I came up with this system when I was looking back at the Englipedia archive. Often activities would be edited later with another user's version. The descriptions of the later versions would be edited into the middle of the existing version, which could make the instructions confusing to follow if you weren't already familiar with the activity. This only got worse when an activity was popular enough to inspire three or four alternate versions.
Now if you have your own version of an activity and you want to share it, you can just upload it as a new activity listing and link it to the one that inspired your version. When anyone's looking at the original activity, they'll see a link to your version and they'll be able to check it out easily. You can explain the entire thing from step one, or just say "Use the rules of the original activity, plus this twist" or "Here's an alternate version of the file for this particular situation."
My hope for this system is that it makes it easier for people to come up with alternate versions of existing activities to suit a wider variety of classroom situations. I've always felt that there isn't one perfect activity for any given situation or lesson - it really depends on the students in the class, the teacher, and countless other factors in the classroom environment. I think it's better to give teachers a wide array of ideas to choose from so they can find what works best for them. I hope this system helps in that regard!
If you want to link your activity to one that inspired it, log in, browse to the activity, and look at the control buttons for the "Link activity to another" button. You should be able to search for the original activity by name, select it from the menu, and make the link.
Also, thanks to another kind user, I was able to list the Sunshine JHS textbooks, so if you're using that series then check it out on the textbooks page! If I've made any mistakes then let me know so I can correct them.