I can't help but think it would be really nice if we could have some training room with dummies or live subjects standing around we could test out weapon loadouts, builds etc. on without having to be forced into live mission just to check one or two things, since that is really frustrating and given we can't swap all items or code on live mission map, but also don't have any combat log to review data feedback on damage changes or triggering amount of stuff like talent tree effects, tokens or what not.
I really think some training room maybe with Omnicron inside where we can swap shards and codes on a fly and observe damage, maybe combat log would really be nice and helpful. Especially if you're either new to the game or somewhat casual that want to be able to come up with something that works for higher difficulties.
On plus side it probably also help with many balancing issues and it be more possible as player to really get some reliable data for things like damage or effect triggers.
EDIT: For functionality point I think of top my head would be.
1. Having Omnicron nearby, where you can swap codes and shards and the stash to grab items.
2. Ability to spawn in dummy enemies of existing races, maybe at data station where you can select faction and difficulty. Also if they're going to be standing inactively not attacking or supposed to act hostile.
3. Some combat log where you can look at data from the test of some kind.