Was just thinking about this randomly tonight. Maybe something along the lines of:
Large ship only
"At the end of the turn if your ship is touching another large ship you may discard this card to board the other ship. The other ship may not perform actions until they repel boarders by rolling a hit or crit"
Modification????
3-5 points or something like that?
Just an idea. I don't play large ships but I thought it sounded like a fun card