it's not pointless because it's the purpose of YaCy to be a search engine technology in itself. What you consider is called metasearch. YaCy is no meta-searchengine.
However, this does not mean that your suggestion is a bad idea. It's just not a working point for YaCy. If you want to have a search to the Wikipedia API and YaCy at the same time, you must put a search page in front of YaCy and wikipedia. There are software modules for that, i.e. searx