I came across some numbers for time to acquire various languages at the sophiagubb.com blog. Some languages have easier grammars than others. Esperanto was included in the study and was the fastest to learn by far.
Although I teach English, I lament that its grammar and idioms and phrasal verbs require years of study for acquisition. I feel that English spelling and character set could be improved. But in terms of making a language that is quick to learn and enables speakers to communicate their ideas after a short amount of study, Esperanto, Ido, or LFN might fill the need better than English.