I love the Good work you do but now i want to buy the Membership plugin and i think if these 2 could work together it could be a powerful plugin.
My suggestion is can you make it so user can forfeit their credit balance to amount set to buy membership if their membership expires or about to expires.
For example :
If a user was a VIP Member and has 5,000 Credit balance and his membership expires the user can choose to pay using 2Checkout Payment gateway, Paypal or Credit balance to extended their membership by using their credit available.
Then the Admin can choose amount to forfeit for each membership level that the user will forfeit.
Thanks in Advance