Marshall Islands and you will work B2B with companies from EU... really?
I don't know if you get money as Affiliate or pay out money to your affiliates, anyway let's imagine you work with someone from Germany that make a payment to your marshall company ohhh first problem, the german tax guy will tell them this is a hidden profit payout as they will not accept payments to Mailbox companies on a Island... the same for many european countries...
You must not only be able to prove to your tax resident country that the place of your Business Operation is in Country X your business partner in Europe must also be able to deal with you without Issues.... forget all this Classic Offshore countries for Europeean B2B companies.
I can suggest Bulgaria and Romania and if you wan't make it the right way rent a small office, hire a local person for daily stuff and so on....