We have two issues/features in this thread that should probably be separated.

1) Custom carts and products.
This means the ability for each customer to see unique products. In the domain name example, the product has attributes which are the domain name. We need this (in our case it's a service name and address, but the same idea). We also need the customer to create this record. Since the customer has the information, it's too expensive and complicated for the customer to provide that to us, we enter it, and then tell the customer it's been entered. Much easier that they enter/edit the information.

2) Repeated/Recurring Billing

In the case of domains and long term (say 1 year) contract, we don't need true recurring billing - the customer just needs a reminder to go back and pay again.

In the case of short term subscriptions, 1 month or less, it should be automatic if you want to keep your customers. True recurring billing. But it seems that if the payment companies are in charge of this, it may not be as difficult as first imagined.

As far as getting paid for the work, for that you have to subscribe to the "Commercial Help Wanted"

http://www.zen-cart.com/forum/forumdisplay.php?f=137

It seems that easytouch2 is onto some good suggestions and ideas, at least for category 1.