To clarify, stat mutators will NEVER return. Baseline stat upgrades at whim begets a meta forming around the most effective stat purchases, leading to greater competition, and shame on others for breaking away from those predefined 'best optimized' routes. Instead, that proof of concept system is now called STRAINS. Strains are a lot more like Heavy's Primary weapon in Team Fortress 2. While you can always use a different minigun, both your alternate choice, and default, are (likely) simple side grades of one another that promote different playstyles.. This is what we intend with strains. Sidegrades that shift up xeno playstyles.
At the moment, we are actively preparing and coding new strains. In time, we would like to have 2-3 strains for each caste member.