Firstly, I must ask one question. Will the Kuva Lich System be updated with new features in the future?
If the answer is no, DE you must remove the system right now. It will only be a pain in the ass for players! The Kuva Lich system in its current form can only be the foundation for further content of the Kuva Lich System. It must be built upon, or it will only become a detriment to the game.
If the answer is Yes, I hope you haven't overloaded yourselves with work. This will need a lot of it and I think you are facing a tight time table to get that done before people tire of the system completely. And here are some additions that I think the Kuva Lich System needs to have implemented in the future. Enemy Kuva Liches
At current, there is one addition I believe the enemy Kuva Liches need. After ranking up to a certain point, the Queens should give the Kuva Lich a fleet of ships that appear on the Star Chart. This addition does two things:
1. It allows players a way to get some of their stuff back. Now players can't be allowed to raid one ship belonging to the Kuva Lich to get all their stuff back, but they should be able to see what raiding a Kuva Lich Ship will get them back. So say if the Kuva Lich steals a relic, the player just has to play the Kuva Ship Mission that lists that Relic as a reward. Obviously a system needs to be in place to encourage players to hunt down the Lich, which can be easily explained as the Lich buffing up security so you can't steal your stuff back (represented by missions giving less stuff back or having ever increasing difficulty).
2. It allows the Kuva Lich to have a Boss Node. The simple reason behind this is it gives players a way to directly attack the Lich when they have figured out the Requiem. It could also allow the Lich to have more personality, with their ship having a interior theme or decorations.
One could also use these to build up Murmurs faster (raiding them for intel), but I think Converted Liches would be better way to handle the Murmur Grind. Converted Liches
As it stands, they have no use in the game at all. There is no benefit in converting. We should be able to utilize those we have converted. And here are a few uses. 1. KILLING YOUR CURRENT KUVA LICH!
Everyone has complained about the Grind and RNG. This is a no brainer. You send off a converted Lich, and in 24 hours (or maybe 12 hours) they've locked your current enemy Lich in an escape pod and fired them into the sun. You don't get any gear for this, but it clears out an unwanted Lich far faster than the grind would.
And alternative is you can put your converted Kuva Liches to work uncovering the Murmurs. This can be as simple as a bonus to the gather rate per lich assigned, or them going off to straight up get the exact information. The later option has potential for events, like your Converted Lich being caught and you have to save them. This has the potential to give the system more depth.
Both of these options help solve the grind issue. 2. Bodyguard
Pretty simple concept. You can have one Lich spawn in with you at the start of a mission and they stay till it ends or they are "forced to retreat." I would suggest they can revive you if you go down. 3. Helping out with other Grinds
The basic idea is they are the new resource drones. You can send them to a sector and harvest resources for you. And given they are powerful soldiers, you can even lend them to the various factions in the game for standing. There are a lot of ways to implement this, as simple as the current resource drones are or something more complex that could add further depth (example: You lend a Lich to Fortuna for a standing mission, but then Nef Anyo sicks the Orb Mother on the lich and you have to go save/fight beside them). Maintaining Converted Kuva Liches
Obviously with what I had just suggested, a limit on the Convert Liches is needed. Firstly being a cap on how many you have. I think this would be best tied solely to master rank and the cap to match up with the Resource Drone Deployment cap as they would effectively replace the resource drones. Retiring a Kuva Lich to make room for a new one is pretty simple, you send them to Iron Wake to join Steel Meridian. I'm unsure if any active systems are needed like we have on the pets. They are intelligent beings, so we shouldn't have to tell them after each mission to get medical attention or to feed themselves.
You could also let players further customize their Lichs cosmetically. Let you colour your edgiest Lich in bright pink.
Obviously there is plenty more that could come from the Kuva Lich System, but these I believe are the first ones that should be implemented to develop it into something the community won't grow tired of.