I think that longer team you should prevent walkovers:
1) No roster can be reduced to less than 10 players. If current sales would reduce your roster to 10, you can't fire or transfer list a player.
To avoid teams getting trapped with a negative balance and not being permitted to sell, always allow a minimum bid ($1000 or $5000) when the roster is less than 12 players.
2) If the lineup for a game is less than 10 players, randomly select healthy players from the roster. If this is not sufficient due to injuries, generate a player with an amateur contract, with inept or worse skills and announcer potential.