I'm certain that this may be one of the first time's this has come up. Not too many people are willing to take the time to take their OD offline, talk players into staying, and then create 25 players. It is VERY time consuming.
Is this truly a factor of there being a limit in database size? When playing in a dynasty with multiple top tier teams, it is very common that multiple players "go pro" or transfer each year. I agree that this is "part of the game." However, it is not part of the game to have teams that cannot properly fill their rosters!
My friends and I purchase this game every year and love the Online Dynasty. It can be somewhat disapointing to actually reach the literal limits of the game.