The sub committees would have no power persay, simply serve as a forum in which countries of the specific regions could voice their concerns and fears, without pressure from outside powers who do not reside in the same region and hold no real sway there. This would prevent conflict from spreading out of a region.
Membership would consist of all nations in the region, including colonies. Thus Italy, for example, would be in both the European and African sub committee, the USA would be in the North and South American committee and the Asian sub committee, etc. Only members of the region would be able to draft resolutions and vote in each sub-commitee. While other nations not in the region could sit in and comment, they would be unable to vote.
The sub-committees would be able to draft resolutions that are supported by a region. This would allow the sub-commitee to sponsor resolutions that benefit their region, giving a more unified backing of resolutions. Or they could, possibly, pass resolutions pertaining only to their area, such as trade deals, arms limitations, or moves to curb certain activites such as smuggling in a specific area. This could be added to the resolution later, as an addendum.