I tried to do a themed run as Monster Hunter. (Modlists: Nex, SiC, QoL)
It failed terribly due to economics. So from that POV I will list the Problems I had and the suggestions.
Problem: It can be really hard to find the Void creatures reliably, compared to Probes.
Suggestion: Visits to Bars giving info on in which systems they have been seen.
Problem: They feel rare, not like spreading pests as described in the bounty.
Suggestion 1: Add "Initial Count of Infested Systems" "Infestation Degree" option via LunaLib, so that the amount of their presence can be set.
Suggestion 2: Add "Reproduction Rate" option, so that if you dont kill all of them in a system, they start multiplying until a limit is reached.
Suggestion 3: Add "Infestation Spread Speed" option, so that they can spread to neighboring star systems.
Problem: Not easy to distinguish types.
Suggestion: The Phase capable ones get some distinct purple glowing organs. The EMP ones get a blue glowing organ.
Problem: Ship AI seems to fail hard on the Phase type since its skill appears to be instant after dephasing.
Suggestion: Add a bit of fire delay to their ranged weapons and skills.
Problem: Ship AI does not seem to disengage properly.
Suggestion: No idea. I dont get why my ships just suicide when fighting.
Problem: Too much all around armor on the small ones. (A 14 FP Swarmhost has more armor than an Onslaught, even the smallest one has armor of cruiser, that is without considering the evolutions that push it into capital level armor)
Suggestion: Instead of normal armor stats, use directional ablative armor plates. (ex: UAF) That way flanking them actually means something and Kinetics dont just tickle them.
Problem: Too high maneuverability. (You capital class has turnrates higher than some frigates) (They have turn rates that keep up with safety override frigates with maneuvering trousters.)
Suggestion: Decrease their turn rates a bit (-20%/-25%/-30%/-35%). That way flanking them becomes possible with fast ships.
Problem: Too steep of a combat curve. Their fleet spawns go from single frigate to two frigates and a cruiser.
Suggestion: Upgrade the current frigates a bit in size(but not stats) and set them to destroyer class. Introduce a few youngling types that each have a degraded version of the adults ability and stats as frigates. That way the player can get used to them and you can increase the number of enemies, so they feel more like pests that grow into nightmares. (tldr: danger in number, but individually weak.)
In total they have potential, but their overreliance on high tech ship systems(phase, emp, entropy) doesnt quite fit the theme of void monsters that are trying to eat you. (Dashes and slowing projectiles would fit a bit better)
Also Hull tanks would fit living creatures better than being Armor tanks.