@rick, I'll need to build an account dashboard for the users but it would be front end.
They need multiple subscriptions because it will be a subscription tied to a product. They can purchase multiple products and the subscriptions will belong to their serial numbers. Just like you would have multiple mobile phone subscriptions under your single user account, each with it's own billing date.
But because of the nature of the service they don't want it to auto-renew, so if they don't renew manually, the service will lapse. With the same analogy, like a prepaid mobile phone.
Coupon code: the product will come with a free membership for the first 1 2 or 5 years but it must not start until they register the serial number of the product. Also, the product user might be different than the one purchased it.
Again, I can build it in Processwire I was just wondering if I could reuse something that's already done for parts of this process.
There are many membership plugins for Wordpress but I try to avoid that trouble. There's nothing of this nature for Processwire, just like there's no complete ecommerce plugin (until Kongondo reveals his, at least).
I just don't want to reinvent the wheel if someone has any pointers for something already in existence.