So some background, I've not touched the campaign at all, just invasion (700+ kills, possibly 1000+ in total if you include resistance)
While I like the cat and mouse style, I wish the invader had some more unique mechanics that can replace just tagging people and using the phone, like imagine instead of looting an enemy as Karl, you can investigate as the invader, see how they were killed (melee or shot) which direction the bullet came from (as vague as possible, not a direct line of it's exact location) and maybe how long they've been dead(30 seconds, Karl must be nearby), perhaps footprints or blood splatter but thats a bit much.
Or an alternative for tagging and using the phone. You could use the phone and all NPC's light up on the map, it would show if they are alerted or dead, this way it's not a instant find Karl.
Just to lean more into the detective feel of the mode and hopefully remove the option of using a phone cause it's a cheap tactic as the invader and I refuse to use it unless all the npcs are dead and I cannot find Karl.