Expansion cards without cover

For use cases where the expansion cards aren’t changed frequently, there could be expansion cards without the whole cover (maybe just bottom and rails).
Would the additional space be sufficient to fit two ports in one expansion card?

Yep, it’s definitely possible to remove the top cover. Some of our prototyping cards are designed that way to accommodate taller connectors. For some cards though, and challenges around fitting multiple ports, it’ll be an X/Y board area constraint.