I'm confused about 1 aspect of your request:
*Supports multiple Merchant gateways
Are you trying to run multiple gateways
at one time or simply trying to ensure that
your gateway will be compatible?
It also sounds like you're shipping physical
items so you wouldl likely benefit from a
dedicated Fulfillment Module that's integrated
with your shopping cart.
There are also some other factors that you
did not specify but are really important such
as ease of payment of affiliates, special
accomodations for Super Affiliates, etc.