So, since my PHP-skillz are on the other side of "good", I was wondering if you'd like to make a couple of (hundred) bucks and create a reduced version of your plugin.
What I have in mind:
1) I create a post
2) Enable a little "registered users can sign up" switch when publishing the post
3) Once this is a sign-uppable post, allow admin to set a number of "classes", as in "advanced, average,beginner" or "men's, women's, youths'" (you know, when I create a tennis tournament, or wish to categorize attendants into different teams)
4) output signed-up users on the post.
That's it. Registered users are easily trackable, all I'd need is a user<->post correlation table, probably.
Will you get in touch with me, please? I can fine-tune a plugin, I can maybe add more features. What I currently can't do is add post-options, save them, output them and add new tables to the WP database.
So if your calendar is all filled up, I'd even pay for the most rudimentary plugin-setup, if you can whip this up before the 28th of december
