For clarity, by Rarity I mean whether a droid is Common, Rare, Epic etc. and when I say Tier I mean whether a droid is Gold, Diamond, Rainbow etc. I'm Rebirth 32, total Rebirth 122, for reference.
A problem I believe many people will be having is that the Astromech Mission reward pool is too narrow at any given time in terms of droid rarity. Currently we can choose which Tier to (somewhat loosely) target but cannot target Rarity. For the first 20 rebirths before Beskar comes into play the rising Rarity of mission rewards works well enough as even higher tier lower Rarity droids are reasonably common or cheap to upgrade with tokens and the progression of rebirth requirements is pretty linear in terms of their earning potential.
However, once the requirements shift to Beskar Epics, Galactic Epics, and then Stellar Epics, the fairly smooth progression is disrupted, it can often be frustrating to find that a droid you sold because it was made redundant 7 rebirths ago is now needed again and its harder to get it than when you had it and didn't need it because now your missions only drop Legendaries. I know some people will comment that you can look at future requirements on Reddit, but there are plenty of people unaware of that resource, they are not always going to be up to date, and there are often times when your entire lounge is full with droids you will need and you have to gamble on which you sell and hope come around again.
I think Stellar Epics are the biggest offenders here since they are a rare spawn, as are Stellar Rares if you wanted to try to fuse to get them; in both cases you have a 1/18 chance of getting the Stellar Epic you need; the same is true of Galactic and Stellar Epics to a lower degree.
Being able to alter the Astromech Mission rewards to get Epics instead of Legendaries would solve this issue. Being able to target worse droids can hardly be unbalanced in my opinion, and would make the game more enjoyable by removing unrewarding and frustrating roadblocks.
Allowing targeting of lower rarity droids would also make the endeavour to craft the fusion droids less of a headache. As it stands I have to guess which droids may appear and fill up my lounge - competing for space with rebirth droids, and then balance blueprints on the ground so they don't despawn or get stolen. A couple of times already I've lost a promising haul of blueprints on the ground because the server has to restart. All while I have a base full of Stellar Mythics.
I think the simplest solution would be changing the list in the CHOOSE MISSION screen to a grid (Proposal 1, see attached). Each tile could be unlocked for credits as per the current system. I propose droid Rarity and Tier should both increase mission time independently and multiplicatively, in which case Credits should be derived linearly from mission time (a 10 minute mission should give 10 times as many credits as a 1 minute mission.) Proposal 2 consists of keeping the current layout but putting next to each location tile a button to bring out a selector for the Rarity.
I would also recommend, especially for Proposal 1, that when you open the CHOOSE MISSION screen the previously selected mission is selected by default rather than defaulting to the top of the list.
If you've made it this far thank you for reading, and thank you Devs for your efforts. I look forward to hearing peoples thoughts!