So many different things to say that come to mind. Bottom line though, and this comes from one of the primary developers at CCP for the EVE Online API's, you have done exactly the right thing with that post.
It is one thing to request additions, improvements, or creation of an API but to make that request and offer a solid and backed reason for it is exactly what the developers at Frontier need. They need to be able to go to their bosses and say "hey, us spending X amount of time on API feature Y benefits Z number of players."
I was actually trying to follow the API development for Elite a while ago but stopped playing and then kind of lost interest after not hearing of any developments in the API. By the sounds of it they are still not offering an official API and this is asking them to do that. The letter is written in such a way that it talks a lot about the market data specifically but the call the action seems to be just general support for third-party developers.
Before I started at CCP I was a third-party developer for EVE Online and the support from CCP has historically been a "whoever has the passion and time to do it does it on their own" kind of thing. So I know how much of a struggle it can be at times to get a company to listen and get even little things done. These days the support from CCP as a company is very much improved and we are working on making it even better.
I personally believe in APIs in games for third-party developers enough that I went and did a presentation at
GDC about why I think it's a good thing to do. I spend a substantial amount of my own time interacting with the third-party developers for EVE and personally I think their work has made a huge impact on the success of EVE Online.
My unsolicited advice to third-party developers is keep on doing what you're doing. Remind them of why you think it's a good idea, show them evidence of people using your tools or sites, and just keep on poking. To Frontier, if you can find a way to make it happen try it. Even the smallest of things can make a world of difference. The number of times I have added a tiny piece of data to an API somewhere and someone has gone and done wonderful things with it... well I have lost count.
Best of luck to everyone involved, I really hope this takes off and Frontier can make it happen. I am a bit biased though.