Just stumbled on this thread today and wanted to share my thoughts.

I had purchased Mage Wars to play with my friends / family 1v1 originally because most of my games were multiplayer and sometimes we just didn't have enough people. For better or worse, everyone I played with liked the aspect of 2V2. As a result, 90% of the games we play are 2v2 teams. We have played about 10 games this way so far. 

After reading the multiplayer rules I realized right off the bat that alternating seats made absolutely no sense. You need to share strategy with your partner. Look over each others books and coordinate a deadly combination. So we sit next to our team mates now.

Another thing we didn't appreciate was the size of the board. With conjurations being zone exclusive we needed more space to spread out if we were running a conjuration heavy strategy. As a result we use two boards and put them next to each other to create a 4X6 grid. We have each team opposite each other in the far corners of the boards. Essentially each full board is a respective team board. This doesn't hurt rushers either because a mage still has the same amount of spaces to reach an enemy mage.

We never combined life because we never had a problem where two mages would completely team up on one. People were too scared the untouched mage would be too powerful. Since we never had that problem we just kept their life untouched and if any mage was killed that team lost since losing an entire mages army / actions is just too devastating. That being said, I actually really like your idea of shared health. While the games we played didn't involve a ganging up on a mage, there were occasional problems. Some games would end up being two 1v1 games in the same arena and sometimes one team mate would get crushed while the other would be doing well. If one died and the other was fine it was indeed frustrating. Combining life pools is a really cool concept that will likely fix this problem. I will probably introduce in my next game and see how our group likes it.

Regarding turn order, we would have all four players roll and whoever won initiation received the token. We would then pass it back and forth to the other team, essentially taking turns by team mates. We did this because having two people on one side go at the same time is just too powerful. Throwing out two huge nukes on a legendary creature before the other team has a chance to react, for example. I personally never liked this method because having three other people have initiation over you could be aggravating. I had tried to think of a solution but nothing came to fruition. I absolutely love your implementation of having it pass between teams and they decide their turn order. This actually adds another layer of strategy and fluidity in a team game. If there's something crucial that's going to happen one side can choose that mage to go first to react. I am absolutely implementing this in our future games as it is the perfect solution.

Finally, for any conjurations that have a ready marker we generally allow people to use as many as they want as long as one of that teams members has an action. For example, a priestess and a warlock are on the same team. If it was the warlocks turn to take an action and they wanted to move and attack, we would allow a priestess to shoot with her temple, if she wanted, and buff with a hand of bim. We found this worked pretty well. It was indeed a bit strong sometimes but the cards were already on the board and players would know if a combo like that was coming and could at least somewhat react with positioning and card choice. Do you also play this way?

We never used the quick cast marker on other team mates turns but that proposes another interesting layer to a team game. I agree, during the initial quick cast it should only be back and forth but during the action stages I think it could work pretty well. I'll have to test it out.

I wanted to say thanks for your ideas. We love Mage Wars and since we only play team games implementing your ideas can drastically improve the game for us.