I'm wondering if anyone has any rules for orbital platforms and/or space stations

In what respect? There are some vague construction rules for void stations right at the end of the Starships chapter. Not very detailed at all, and focused on combat, but enough to make a start.

There is an example space station in the book - however if you want a different type just take a ship and take off it's warp drive and geller field, make the guns keel guns and add extended supply vaults... Imperial tech is very hardy and I can imagine that many installations started off as ships hulks that were simply tethered to asteroids, etc...

As you might be aware, I'm compiling Starship rules. My next projects will be:

Mechanicus Explorator ships and an assortment of Teleportarium rules from this forum.

Space Station translations from BFG

and last, Xenos Ships.

It'll be 3 different articles and not necessarily in that order. So, yes. If someone posts their version before I'm done, I'll credit them and probably swipe all or part of it for the article.