Since this change would mainly be aimed at effecting teams later in their TV development, and to encourage more interesting skill picks, I thought it might be best to create established teams, say 140 TV. No Inducements. To keep some kind of realism let's say your normal Improvements must outnumber the doubles and no stat increases.
The tournament would use a format similar to the Gore Grail, with small groups playing games simultaenously.
The change would be as follows:
Block (General Skill)
A player may use Block to stay on their feet if your opponent selects a Both Down result when someone throws a block at them.
Sack (General Skill)
A player may use Sack to stay on their feet if you select a Both Down result when throwing a block.
I'm thinking that Dwarfs, CDs and Zon Blitzers keep Block, and everyone else who starts with Block replaces it with Sack. This is open to negotiation / suggestions.
This won't be supported by the PBeM Tool, so you'll need to make a manual roll every so often.
Who's interested?

Cheers
Joe