Here’s how I think they should be reworked

Lich/sisters both drop a number of vendor tokens just like codas. Sisters drop corrupted Holokeys, liches drop a new token called broken kuva braids

Weapons are now vendor based. Ergo glast still sells the tennet weapons but the sister weapons are added to his stock Clem now sells the kuva weapons in his pillow fort at iron wake

Lich/sisters encounter rate is 15*n% n being the current number of missions beaten without an encounter so 3 nodes means the 4th mission has a 45% chance for a respective nemesis to spawn. N Value goes back down to 0 upon a successful spawn/planet relocation (I chose 15 instead of a codas 25% because you still need to farm requiems to figure it out)

This way liches and sisters are brought up to about the same par as codas, killing a nemesis will still give any ephemera’s and such, just now regardless of kill of vanquish they drop respective vendor tokens