Steel Path can be rough on [Mesa] and her ol' [Regulators], especially on Peacemaker. This build, alongside the accompanying [Regulators] build, aim to alleviate this problem.

NOTE: You'll want to use the Regulators Prime build here, as it goes with the build for [Mesa] used here.

Aura & Arcanes

[Steel Charge] is used to save Forma investment, but can be exchanged out for [Pistol Amp] or other auras should you be willing to invest more into her. I'm personally chronically short on Forma, as are many others, so that's why this is a thing. [Mesa's Waltz] prevents her from being a stationary target, as you'll want some space to maneuver if necessary.

Arcane Energize can be done without if one doesn't have it (Arcane Precision substitutes fine), but the Zenurik focus tree or other sources of energy will be needed - a strong energy economy will help you stay aggressive and cleaning up enemies wherever you go. Arcane Velocity is to augment her 4's fire rate, and I strongly advise keeping it.

Helminth Modifications

Eclipse takes the place of Ballistic Battery. Roar works too, but not nearly as well. The sheer damage increase offered here makes [Mesa] a force to be reckoned with deep into Steel Path, even more so than she was previously.

Stat & Mod Configuration

This build largely speaks for itself, but let's go over the stat choices on [Mesa] and explain why they're set up this way.

Our Strength needs to be high, very high. This ups the damage multiplier on Peacemaker and the damage increase of Eclipse. [Blind Rage] and [Umbral Intensify] serve this purpose.

Range is negligible. It's practically a dump stat here. [Narrow Minded] covers this nicely, and lets [Mesa]'s other abilities last a while.

Efficiency is crucial here, as going negative is a terrible idea. [Fleeting Expertise] and [Streamline] work in tandem to keep you positive, with the duration loss being offset from the aforementioned [Narrow Minded] under wraps. [Primed Flow] gives you a large energy reservoir to make managing output easier.

Duration gives our Eclipse a duration of 49 seconds, which makes energy conservation easier a you'll cast it far less often. Also helps out Shooting Gallery and Shatter Shield, but primarily benefits Eclipse. [Primed Continuity] further offsets any duration loss we incur from other mods.

And finally, [Adaptation]. While not of benefit to any of our stats directly, running without it is dangerous for a glass cannon like [Mesa]. It gives her much more survivability, and combines with Shatter Shield to give her some reasonable bulk. Don't get too comfortable though, because she's no tank. You will have to be active in order to keep her from going down more than Comcast's internet services (hard to beat that, but you get the idea).

Wrap Up & Notes

To conclude our build, let's go over substitutes you can use for stuff you might be missing.

Mods

Primed Continuity/Primed Flow: Can be exchanged for their non-primed counterparts
Umbral Intensify: Swap out for normal Intensify.
Mesa's Waltz: Any of the Drift mods (except you, Cunning Drift. -.-) work fine.
[Adaptation]: [Vitality], I guess? You'll be a literal glass cannon, so good luck.

Arcanes

Arcane Energize: Zenurik's Energizing Dash, Squad Energy Restore (a lot of them), or kidnap a [Trinity].
Arcane Velocity: Arcane Precision to offset the fire rate loss.