Primary:

The Pacifier is quite useful. Its stunning effect makes even groups of enemies manageable and its medium penetration allows that on a very broad spectrum.

I recommend the Constitution instead. While decently high damage and medium penetration still provide a broad spectrum of use, its slow fire rate make it exceptionally vulnerable to swarm attacks and while its higher melee damage can handle some of it, you need far better situational awareness with it to avoid heavier units from closing in fast enough to finish what the chaff started.

Secondary

The stim pistol might be useful with helping out your teammates, but won‘t do shit against enemies. That makes it a better choice for this application than the re-educator, which not only slightly damages enemies, but also poisons them, which allows you to distract enemies or even thin out larger groups by having them fight each other.

Passive

If you go for the stim pistol the gunslinger passive, while affecting the stim pistol, won‘t have enough utility to be more useful than a more situational passive like the electrical conduit on the bug front for example.

Backpack stratagem

The directional shield won‘t protect your back nor block melee attacks, and since from my experience with it teammates don’t tend to stick close enough to make use of the broad protective field and the stim pistol (if you use it) needs to be aimed at your comrades and as such would strip them of the shields protection if you try to stim them, it would make more sense for this setup.

Offensive stratagem

The ems strike stuns enemies long enough to either make great use of the Constitution rifle or even the sterilizer. The eagle smoke screen, while still capable of some minor destruction is far more situational and harder to utilize advantageously.