I have been using Mr. Bistro's Advanced Rules and they are awesome. My friend and are going to try a small league (4 people) and see how that goes.
I changed some of the MVP skills to better fit my passing, catching, interception rules.
I dropped the Pick up and Throw skill because I didn't really feel like it fit the character of the game. Works nice in Blood Bowl, but is too goofy for Battle Ball
I also dropped the Steady Hands and Long Bomb skills.
To replace these I adapted the Pass and Catch skills from Blood Bowl. They fit better with my Passing / Receiving rule variant.
Pass: A character with Pass may reroll 1 die 1 time, either their character die or the brown passing die, when performing a pass action. This new roll is final and may not be rerolled again. This may be combined with another reroll (like Filthy Cheat skill) to reroll both passing dice.
Catch: A character with Catch may reroll their character die 1 time when performing a catch / receive action. Catch may not be used to reroll a failed interception. A Catch reroll must be made before any interception rolls. This new roll is final and may not be rerolled again.
Intercept: Lightning fast reflexes have made this character every throwers nightmare. A character with this skill may make a move action to intercept the ball when the opposing team is attempting to make a pass.
This character may make a half move action and move in between the passer and receiver. This move takes place after the passer has successfully rolled passing dice. The Interceptor may only move if doing so will put them between the passer and the receiver. They may not move adajacent to any opposing character. Only 1 character with Intercept may use the skill on any pass
In play testing they all work fine. Runningbacks with Intercept are a little scary with the 10 move. This is why I made it unable to combine Catch and Intercept, though it is fun. We may drop the Runningbacks Intercept move to 8.
I also added two skill just for Heavy Tackles when they roll Built Like a Tank or Dead Hard
Reach (replaces Built Like a Tank for Heavy Tackles on the skill chart): Using his wide reach, a Heavy Tackle with this skill covers a greater distance when Blocking. He may Block (not Tackle) players up 2 spaces away instead of 1. This may only used against players on his sides and in front of him, not behind.
Intimidation (replaces Dead Hard for Heavy Tackles on the skill chart):
This player is extremely intimidating and causes opposing players to tremble in their boots. All opposing players within 3 spaces of the Heavy Tackle must subtract 1 from their pass, catch, and interception rolls.
I changed Filthy Cheat to give it a bit more carnage.
Filthy Cheat: This player knows every trick in the book. When making Piling On rolls this player adds 1 to his die roll.
Finally for the skills I changed the numbers around to make better skills harder to get. Rampage and Filthy Cheat are 2 and 3. Built Like a Tank and Dead hard are now 11 and 12.
I also adopted rules from Blood Bowl for MVP rolls, earning MVP points and Serious Injury rolls. These require a bit more record keeping, but can add some more depth without much difficulty. I probably wouldn't use the earning MVP points unless it was in a league situation with more than 4 people. MVP rolls would rack up too much
For the MVP rolls first roll 2d6. On a 2-9 your player gets a new skill. On a 10 add +1 to the player's Movement rolls (not half move) or new skill. On an 11 add +1 to player's Agility rolls (Passing, Catching, Intercepting) or new skill. On a 12 add -1 to the player's Strength rolls (Tackle, Block) or new skill. No abilities may ever be modified by more than 2.
For the Serious Injury rolls, roll 1 d20. 5 or higher the player has recovered and is fine. Add 1 to the player's SI rating. On a 4 the player gets -1 to all movement rolls, Half move and Intercept skill move. On a 3 the player gets -1 to all pass, catch and interception rolls. On a 2 the player gets +1 to all Block and Tackle rolls. On a 1 the player is dead.
For earning MVP rolls, you could simply use the Blood Bowl rules straight from the rule book. Maybe drop the Most Valuable Player award.
Again this stuff would make record keeping a bit more technical, so maybe it takes from the short and sweet element of the game.