I think Nimon has the answer right on. It sounds like you do not so much want to DM, but rather would be happy to provide assistance to the individual running the game. The challenge in such a situation is, of course, making sure that you do not know too much and can enjoy the sessions as a player. If, however, you intend to simply be an observer (as I imagine this dislike of talking also extends to time as a player) and record keeper ... I see no issues/pitfalls at all with the two of you working together. Other than the standard pitfalls of working in a group that is (competing ideas, compromise, etc).
On a side note, I have been a part of three campaigns in which all of those participating in the campaign took turns at being the DM. We rotated on a per-adventure/per-module basis (so a rotation about once every 2-3 weeks playing once/week). There were 5 of us ... so you basically got the fun of being a DM for 2 weeks out of every 10 and the other 8 weeks you got the fun of being a player while having time to really build a great next module/adventure for when your turn came around. Those were great campaigns. Not linear at all ... multiple story lines keeping us all interested (with cameos or bits of stories crossing DMs) ... and a relaxing pace for DMing.