The question seems to be referring to the presence of administrative agencies in government. With this in mind, I think that a fairly compelling argument could be stated that there are a sufficient number of administrative agencies. Some might even say that we have too many federal agencies. One does not have to go very far to hear the cries of "runaway government" on the grounds of excessive administrative agencies. I only bring this up to simply raise thought with regards to the premise of the question.
If we were to create another agency, I would suggest that one specific agency should be created to address the needs of young people. We seem to be at a point in American education and society where we stress children to go to school and go to college. Yet, as has become evident with drop out rates and disenfranchisement of many young people, some enter the bright line of being 18 without much in way of prospects or hope for the future. Rise in criminal activity like gang shootings and affiliations as well as greater disenfranchisemnt can be traced to a perceived lack of promise in our young people. In making the assumption that the question makes (Government agencies can be effective in addressing problems), I would suggest that there could be a revival of the New Deal's National Youth Administration. This program and agency was designed to work with an at risk population of young people from ages 16-25. The agency was "focused on providing work and education" to a group that was largely ignored during the Great Depression. The belief was that the nation is strengthened when disenfranchised youth is empowered towards productivity.
Bringing back this agency and ensuring that its outreach is in both rural and urban areas could prove to be quite empowering for youth that might not feel that there is much in way of promise and possibility. Certainly, it would be unrealistic to insist that one government agency radically transforms all at- risk youth. However, it is fair to make the presumption that some could be helped by an agency that seeks to provide job training opportunities, networking with members of the community, and create avenues in which young people could see themselves becoming productive contributors to the social fabric of a liberal democracy. There could also be educational initiatives in both vocational training or preparation for entrance into advanced educational institutions. In developing an agency designed to meet the needs of young people as a targeted demographic, a type of National Youth Administration might prove to have some impact on young people who might otherwise go ignored and silenced. I could see this as a potential agency that could be created if we operated under the idea that there are not enough administrative agencies in government today.