I don't think it would resolve anything.
Most plots are the vision of one GM, who might then be supported one or more co-GMs. That is to say a tiered hierarchy, such as TFL. It's Gallant's plot but run by Kim and Kokuten at the moment.
But there are a minority of plots where there are two co-equal GMs (NSS Venus with Shotty and myself). In which case, it is perfectly acceptable to call either one of them a co-GM.
The concept is problematic only in that it has two (or more) definitions, depending upon the GM and circumstances.
Putting co-GMs and primary plot GMs on the same level in terms of forum access and authority is one part of a solution. That way, we can increase the pool of potential GMs. The major difference between a GM and a "co-GM" is really the circumstances of the plot and the definition which those people work under. Despite this circumstantial factor, I don't think anyone would argue that Co-GMs deserve less access, authority, etc than the Plot GMs.