Hi, I suggest to use s2member plugin for users/groups/subscriptions managment. It allows creating addon plugin without customizing core plugin code and have lots of managment and controls options. My quote is for integrating and customizing this plugine, you will need to buy a license of s2member. Will be finished in less than a week.
Please check my profile's feedbacks and reviews to see the proof of my experience and expertise in Wordpress. There is more than a hundred of excellent reviews and all of them received the highest ratings, all rated 5 out of 5 with 97% completion rate, that is really rare case when ALL employers are fully satisfied! Please compare to other freelancers ratings, their average usually is 4.9 or 4.8 and 60-80% completion rate meaning that they failed sometimes.
I have successfully completed hundreds of different WP projects starting from minor theme or content updates to huge and complex WP plugin development and dozens external API integration tasks. I have 11 years experience in Web Development, 5 years with Wordpress. My favourite technologies are PHP, MySQL, HTML5, CSS, JavaScript + Ajax + jQuery + libs.
Comparing to other freelancers who are spamming with their bids I am actually reading your project description and bid with precision only on projects I like. I am located in Latvia, North Europe and I work only with employers located in Europe and North America.