Esperanto is an invented language created by L. L. Zamenhoff. It was deliberately designed to be simple and regular. There are no grammatical exceptions to be memorised. It is easy. That is the number one reason that it should be considered for the position as first second language someone is taught or learns. Not that much time needs to be dedicated to teaching or learning of Esperanto to experience the tremendous benefits that it can yield. In fact, just two weeks of study can put a learner at a distinct advantage in learning another language. What are these “tremendous benefits?”
First, learning Esperanto first allows students to be introduced to the concept of learning another language. As an added bonus Esperanto is regular so there is no need for students to fret about weird grammar rules and exceptions. They can focus solely on communicating in a new language. Furthermore, much of the vocabulary comes from the Romance languages and Germanic languages, meaning that it is not only easily recognisable, but gives students an advantage if they go on to study a Romance language or a Germanic language.
Another advantage is that with each language one learns the next becomes a little simpler. Therefore, learning Esperanto makes learning any other language just a bit easier. Learning Esperanto can introduce students to new concepts in grammar (without exceptions) and the skills to learn another language.
In the end, the best part of teaching or learning Esperanto first is that one need not be considered with becoming fluent. It is true that there is a vibrant Esperanto community; however, most people probably won’t end up using Esperanto, but that doesn’t matter. Learning it first will equip them with the skills to learn a third (or real second) language and beyond. Maybe teaching Esperanto first will ignite a love of language in students and that is always a good thing.