[StevenB]

I agree with MathKing and Lil' Lavery that a 6-team cooperative effort could be very fruitful. Let's try some numbers, ignoring the tower bonuses for the moment.
1) Suppose that in a "normal" round, the Red Alliance can score 8 points against the Blue defense, while the Blue Alliance can only score 3. Red gets 8 + 2*3 = 14 seeding points; Blue gets 8 seeding points.

2) In a second scenario, Red scores 8 times, 6 for Red, and twice for Blue. Blue scores 3, making the final score 6 to 5. Red gets 6 + 2*5 = 16; Blue gets 6.

3) Now suppose the alliances cooperate - this makes both sides far more productive. I'll suggest that Red can now score 12 balls, while Blue scores 4 (in Red's goal). Red gets 16 + 2*0 = 16 seeding points; Blue also gets 16 points.

I think playing this way is highly advantageous for both sides. Seeding-points wise, option 2 is the best win for Red. However, option 3 doesn't come with the risk that Blue could make a sudden comeback and win with the help of Red's two goals. This is where the tower points might really make a difference. If Blue had a stronger defense, the balance tips further in favor of option 3. Even if you can beat an alliance handily, having their help might still put you ahead.