I used to play that format back in the days, and we definitively did not allow the color hosers (they unbalance the games too much and some colors have exactly no answer to them). We allowed allies to block in combat because this allowed very fun diplomaty/tactical.
Here are some hints, IMHO :
- Black deck should be either the classic control black or a more suicide one. Both are quite iconic and Old school deck lists can be a good start. I would add a few random slots such as royal assassin and/or sorceress queen for the flavour (actually you could do the same for each color).
- White could go wheeny obviously.
- Green could ramp into Fatties (force of nature, craw giant, ...). A friend of mine used to play that and he could have a force of nature attack at turn 3 quite easily, maybe a less all-in version could be designed. Green weakness was the lack of flying creature.
- Red could go into Goblin deck as it was the first tribal deck that really succeed in tornaments but i am not sure it would be strong enough in such a format (blood moon is not good here). Blasts spells are a must but it would be more fun to have blast be only a tool to help a main strategy.
- Blue should have a lot of control spells (counter, control magic, ...) and a few good flying creatures.