After playing with it a bit, I have fine tuned it a little and shall update the main thread that Lord0fWinter linked to. However, I'll also post it here for your convenience.
Spell Rules
The Unique trait and Epic trait both apply to the whole team. Thus, if your team mate has a Unique spell in play, you may not play another copy of that spell. If your team mate has an Epic spell in their spellbook, you can not also have a copy of it in your spellbook. You also can not put Mage Specific Abilities on spells that you do not control, such as making your team mate's creature into your Pet, or putting Runes on your team mate's equipment (even if you cast the equipment).
Board Setup
Using two Arena Boards create a 4x6 Zone Arena. Labeling the Rows as A through D and the Columns as 1 through 6, the top left zone would be A1 and the bottom right zone would be D6. Team 1 would then start with their mages in B1 and C1, while Team 2 would start in B6 and C6. This allows team members to start near one another, yet with enough room so that they don't compete heavily for conjuration space. They also start within 5 and 6 zones of their opponents, which is comparable to a normal match and allows rush strategies to be just as valid, if not more so, as normal.
Shared Initiative
Initiative shall be shared by team members. When it is your team's turn in initiative order, only one of your team members may act. Decide as a team which team member gets to act whenever it is your team's turn in initiative order. You may not use your Quick Cast Marker unless you are the team member currently acting.
Shared Life
Each team shall have a Life total equal to 75% of the sum of the two mages that make up the team. Any damage done to one mage is cumulative against the entire team, and any healing done to one mage removes damage from the team. Thus it is possible for Mage A to take all the damage, and Mage B to still remove it by healing himself instead of his team mate. Consider this an improved version of Life Bond. For those who don't wish to do the math of percentages, I have calculated 75% of each individual mage at the end of this article.
Mage Life Conversion Cheat Sheet
Convert each individual mage using the chart below and then add the two team mates together. Round the total to the nearest whole number.
38 = 28.5
36 = 27
34 = 25.5
33 = 24.75
32 = 24
30 = 22.5
Conclusion
I have played several games using this setup and it works pretty well. I will warn you that this does not protect against every possible scenario that may crop up, as some things do occasionally raise questions during team play. Unfortunately there are not official answers for most of these questions, and I would suggest you just house rule them as they appear. I wish you luck and glory in the arena.
