AT BWI your at a pretty large disadvantage when it comes to this.
BWI is a common SW connection city. Chicago Midway would have the same problem.
For both EBCI or normal checkin you check in 24 hours before your first flight.
So lets say 2 people are flying from BWI to Orlando at 12 noon.
A is flying from Albany to BWI to MCO The Albany to BWI flight leaves at 10 AM.
B is flying from BWI to MCO directly
A will be ahead of B every time. Because A got checked in for the BWI to MCO flight when they checked in for the first flight, 2 hours before. Doesn't matter if the person is EBCI or not.
Not only do you have a worst boarding position going from BWI, but the same boarding position is generally worse on a flight leaving from BWI unless its first thing in the morning because there are probably already people on the plane before you board.