What problem is this trying to solve? Is it the cost of language interpreters? That will probably soon be solved by technology. Is it the lack of a "demos"? That would only be solved if everyone in the European demos also learned English and all local politicians only spoke English, which is, ahem, unlikely to happen ever.
If countries offered Government services including education in English, it would hugely assist the movement of people and capital throughout the continent.
Consider: you are from Spain, and have been offered a job at a great company in Germany. You will speak English at the office and probably get around the city speaking English. But: your children need to learn German, fluently and immediately, in order to continue their schooling?
An official EU English would help pave the way for National Governments to offer services in both the local language and English.