we've used this rule for a year and a half now, and it is very popular.
First let me point out that the rule may not seem particularly fair. The rule to some extent prevents bashing teams from shutting out other teams by "eating up the clock". And I know that "eating up the clock" is a perfectly legal tactic.
No doubt about it.
The thing is that this makes for some very un-exciting Blood Bowl.
Reducing your opponent to 4 players and then waiting for the half to end before scoring simply isn't very exciting. Effecient - yes, exciting - no!
This is probably why the rule has become popular in my league - even with the coaches of the bashing teams!! And no - it hasn't meant that the league has become dominated by scoring teams. Not by a long shot.
The rule: Conceding a touchdown:
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Whenever a team is outnumbered by at least 3 players on the pitch at the very beginning of the teams turn, then it's head coach is allowed to concede a TD. The team's turn ends immediately.
The outnumbering team gets to take its next turn as normal, but at the end of that turn its head coach must decide whether to "accept the TD" or to "delay the game".
*Accept the TD: The player with the ball automatically scores a TD. If the ball was on the ground (or in the hands of an opposing player), then a random player on the pitch from the outnumbering team scores the TD.
*Delay the Game: The outnumbering team immediately suffers the effects of a pitch invasion (d6 inury rolls). However, a TD is not scored, and play proceeds as normal.
(The conceding team may concede again if elligible, or may play on if they prefer)
Fun for everyone!

Martin