Actually there are already 3 commands (Northern, Central and Southern).
Based on what I know as far as the challenges with this split is that if there are no direct troops under your command, the post remains ineffectual (something that poses a problem for the Pakistani Joint Chiefs of Staff as well). The regional commands are commanded by 3 star generals (Lt Gens) but right under them you have Corps that are also commanded by Lt Gens. So there are some problems with having the appropriate hierarchy in the regional Army commands that provide for appropriate seniority and authority to the regional commanders over Corps Commanders.
I am not sure as to what the solution is, but we may start seeing 4 star generals (as in the US Army's regional commands) leading these 3 commands. The challenge at that point becomes the hierarchy between the regional commands and the CoAS. So this has to be worked out among many other issues like logistics and planning for each regional command. It will take a while for the RCs to shape up if the PA sticks with the idea.