This stuff is probably infinite. How exciting! The scope of arcsecond.io is expanding. And I have additional ideas for the future... In the meantime, here comes basic support for Data Archives: ESO's, MAST etc. I had a quick connector already written for ESO programmes summary, hence that's the only thing available for now. For instance:

api.arcsecond.io/1/archives/ESO/073.D-0473(A)/summary/

But more will come! I am already working on the access to data sets (hopefully, with some local meteo data...), in a completely integrated manner, with access to objects, observatories etc.