I have an Web API developed using the http methods as they were intended[0] by the authors. Now I need to enhance the GET based API calls with support for batch requests. It turns out that there is no standard method to encode more than name -> value pairs in the query string. Everything is framework, language specific. So if you need more(e.g. an array or a nested data structure) than name value pairs you better avoid GET. I hope this helps anyone who starts a new Web API project.
[0] https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html