I'll repost some of the early suggestions here:
- Planeshift - select a plane card to start on for your turn and all rolls go against the owner of the plane
- Vanguard Avatar - vanguard avatars are legal (may have an extra slot for it, might not)
- Planeswalker - You can have 4 cards but one has to be a planeswalker
- Two-headed giant - this one would get crazy
- Limited omniscience - Each player begins with X Treasure tokens in play
- Landfall - basic lands all have some sort of landfall ability
- Conspiracy theory - Each player starts with a conspiracy of their choice in the command zone
- Like a flash - all spells players cast have flash
- Unexpected potential - I can't see it really being used much given we have the dual lands already so you need to use storage lands for this to even matter.
- Hymn of the wilds - no instants and sorceries but slightly bigger creatures seems okay but a bit boring in that it restricts rather than given more options and any neat ideas are just ones that wouldn't hold up against sorceries.
- Double Stroke - could be nifty, likely to be dominated by discard and anti discard effects. Multimodal spells could be useful
- Brago's Favor - seems kinda dull. I guess it enables some spells quicker that would just be out of range and make the iguana playable
If we went for this sort of path, I think I'd prefer it as each player having a 3 card deck plus a conspiracy/hidden agenda of their choice
- Trinisphere - land destruction would have to be flat out banned as otherwise running 2 destruction lands locks out everything but bazaar of baghdad grave recursion decks.
- Mana Flare - quicker 2-drops with an extra slot. Might see the iguana be playable again as above
- Wheel of Sun and Moon - potentially are more interesting one but depends if people find exile effects instead
- Extra basic land - probably similar in effect to mana flare but with some intricacies allowing 2 multicoloured mana with a mox T1 with 2 cards remaining
- Creatures can't attack - bigger change, could be fun. A couple of decks stand out but it should still have variety
- No creatures - see above but tokens can attack and you lose the creature effects
- Waste deck - had a lot of variety last time but I don't particularly want to revisit one from the old thread this early
- T1 discard - why? Why would anyone choose anything other than the one that comes back from the graveyard or one that shuffles itself back into your library
Also, starting life totals of any less than 11 will probably need to ban Chancellor of the Dross.