Given the complexity of the matter, but I wonder if it wouldn’t be worth integrating the Pro API from Enedis on the Gladys Gateway side?
I can take responsibility for Gladys users 
I’m not necessarily confident about integrating an external API set up for free, which may not necessarily be sustainable in the long run.
If the service is no longer available, for Gladys users it will be Gladys’s fault, which is a mediocre UX.