This is the response I got from Paypal:
Thanks for your question regarding subscriptions. If you have an
existing button on your site and you sign up for enhanced recurring
payments you would want to make a new subscription button so that you
are able to update your site, it will not happen automatically. You
should be able to use the standard subscribe button for normal
subscriptions or enhanced recurring payments. Here is some info about
the differences with enhanced recurring payments.
The Enhanced Recurring Payments service is a premium option for Website
Payments Standard merchants who use Recurring Payments and
Subscriptions.
Enhanced Recurring Payments options include these 3 product categories:
1. Guest Checkout – enables buyers to pay for recurring subscriptions
using a credit card instead of a PayPal account.
2. Installment Plans – similar to a flexible payment plan that allows
your customer to make a purchase from you and pay you in 4 or fewer
installments -- e.g., $1K after 15 days, $2K after 30 days and $3K after
60 days
Why use Installment Plans? Customers are more likely to buy
certain products and services if they can pay you in deferred
installments. The advanced features in our Installment Plans allow you
to sell a product, and then charge up to four installments within 12
months.
For example, a customer buying furniture can pay 50% after 15
days, 25% after 30 days, and the balance after 60 days. The money is
automatically transferred from their credit card or PayPal account, and
you’ll receive an email notification when each installment is paid to
you.
Installment plans do not allow you to charge interest or fees.
3. Automatic Billing – automatic billing allows you to charge your
customer’s PayPal account, bank account, credit card, or debit card on a
regular basis for an agreed-upon amount.
Why use Automatic Billing? You can use automatic billing when your
customer’s payment amount varies each week or month, like your utility
bill. You and your buyer agree on the maximum amount, as well as the
duration of payments. You automatically receive the money from your
buyer for the duration of your billing terms.
I'm not totally sure I follow, but it sounds like your plugin should work, right?