2) How far are we going and where are we stopping?
I know you've probably elaborated quite a bit on this, and I'm probably just being stupid and not realizing it, but could you elaborate on this?
Also, as far as I can tell, I think there really aren't that many limitations that we need to keep in mind. Just:
- No cards that have a mechanic like Flooding since it would partly rely on the opponent having FM cards of their own to not be OP
- No cards in Water to create the possibility of single element instakill of any targetable creature (besides Water ones, but that's not the point)
I mean, are there really any more besides obvious ones?
The major limitation is "creatures do not move on their own, yet". This severely restricts hostile field manipulation(since card taxes are bad) unless we change creature mobility. Both sides have merits but we would need to decide on how far we want to go on this(including the option of status quo).
Flooding is related and will be similarly restrictive but less so than the general problem. It is more an example of how restrictive we would have to be if we avoid changing creatures.
There are other decisions to make as well(like how many effects can a tile have, and do we add more passives to existing creatures)
A different way of saying the same thing:
Field Manipulation is a new kind* of threat(what I will be talking about) and a new kind of boon(we can gloss past this for now). Unlike most existing threats, there is almost no way to combat this threat without reserving space for the boon half in your deck. we can choose to add this kind of threat(and thus require most decks have a way of dealing with it) or we can choose not to add this kind of threat. If we add this kind of threat, we can either just accept the card taxes(most decks would need field manipulation cards) or we can spread small countermeasures among a large number of existing cards(creating an alternative but weaker counter to this new threat).
Technically it is many different overlapping kinds of threats. We will see more as we go along. For now we see "move or be rendered irrelevant(flooded tiles, lava tiles, buried tiles, pacifism auras, grouped and fireball'd)". However there will also be other things like "killed by creatures/permanents/tiles I can't destroy since they are on my side".