I remember a session with a similar idea. John Laviña posted an idea of an app where you can report problems in your close vicinity and potentiate local authorities to solve them. Your idea feels like an upgrade of this app with a national note. I think it could be smarter to start with small local issues and gradually build up towards the national and more general ones.
Problem - it will end up in a list of non-novel problems
One reason is that citizens are not specialists in all fields such as employment, business, agriculture, taxes, etc., but they all are specialists in reporting a hole on the pavement close to their home. A platform that collects opinions of the citizens on problems like this would end up solving thousand of small infrastructural issues - a job that is currently done by the local authorities and could be covered with the above-mentioned John Laviña's app. On the other hand, citizens reporting on bigger and more general problems should maybe have some expertise, or else it will end up being a list of common and non-novel problems, which are often very hard to solve.
Solution - starting small and building a app reputation, citizen engagement and feeling of importance
Starting from small local problems could empower citizens to act and engage them more, since their local problems could be solved faster and more efficiently. They could see the progress with their own eyes. Then, the members who are very active could get an invitation to courses and conferences (like Google Maps contributor program) where government bodies, high institutions and experts discuss and debate current issues of wider reach (national level). That way a community would get a lot of experts (influencers) familiar with the situation and could think of and promote new solutions. Citizens would rather listen to them than the authorities, which would also make this platform an independent, peer-driven platform for communication of the local communities.