Perhaps what you want is a range of boards with many combinations of features. Some with 4xethernet, some with 2xethernet, some with PCIE and 1xethernet, some w

Perhaps what you want is a range of boards with many combinations of features. Some with 4xethernet, some with 2xethernet, some with PCIE and 1xethernet, some with M.2 and PCIE, some with M.2 and 2xethernet, etc. to fill out that big matrix of combinations. But is the market big enough for such a huge range to be economical? Some of them have PCIE which you could connect a network card to. That seems like a more practical way to allow flexibility than having a lot of special purpose boards.