Unfortunately that won't work in some cases like commonsMedia or url. If you
look at 
https://www.wikidata.org/w/api.php?action=wbgetentities&ids=q76&format=jsonfm:

                            "property": "P18",
                            "datavalue": {
                                "value": "President Barack Obama.jpg",
                                "type": "string"
                            }

We could probably implement a fallback for the ones that will work like entity,
coordinate and time, and emit a warning like "P288 does not exist"

This error is probably rare to run into since the datatype is cached forever,
but most scripts need to re-cache everything because the ids went uppercase.