I also made a thread theorycrafting a Cult Mechanicus class! Check it out!
I hadn’t thought about keystones, so I’ll share some keystone ideas as well:
Keystone 1: Optimized Circuits: Provides a small bonus to all stats. Add-on nodes either increase the stat bonuses or applies bonuses to teammates in coherency.
Keystone 2: Neurological Override: Enemies you tag become mind controlled for 15 seconds, and start infighting. Mind controlled enemies take less damage from you and your allies, gain a green tag outline instead of red, and receive a large damage and speed boost. You cannot tag a new enemy if you have one already mind controlled. 45 second cooldown. Add-ons allow mind control to last 10 seconds longer or spread to enemies near the tagged target at the cost of 15 seconds of additional cooldown.
Keystone 3: Ablative Armor: Start each mission with 3 stacks of Ablative Armor, which nullify health damage taken and are then all consumed. You have a 10% chance to gain a stack of Ablative Armor on Elite kill. Max stacks 3, effect only triggers when you have 3 stacks. Add-ons increase chance to gain stack on elite kill, or allow gained stacks to be transferred to a random teammate in Coherency if you are already at maximum.