Well, it seems that the only remained “likely things” to be added to the game are the “Artifact Recovery” music, The Comet/Supernova mission type and its music.
But, I’ve revised my previous idea about Mission Type: Exploration. It may (with a high probability) pushed to after the final release because of its "major"ness, but an idea is an idea 
One of the most issues taken on my initial idea, was that the intraplanetary (= inside the planet) layout is unlikely to be procedurally generated. Now what if the textures would be always in the same order (= we have the same layout always), but with different chickens based on difficulty (much like Squwak Block).
There are many types of planets (Gas giant, Artificial moon, Alien world etc.), so there could be a certain likeness (and even new boss!) for each planet type. Three of them - obviously - are assigned to the three CI5 missions:
Epsilon Thalassus (CI5) → Terran planet
Gamma Chthon (CI5) → Barren rock
Eta Astropelecae (CI5) → Frozen wasteland (The lightning storms make sense.)
As now there is no “artifact” to be collected, the boss names may change.
P.S.: @InterAction_studios , are the names Thalassus, Chthon and Astropelecae registered on the star system names? 
I haven’t find them yet 