Rebuilt a few times:

First Change after the update to [Reflect] the new capacity.
Inspired by THeMooN85's build. Rearranged and adapted slightly to my taste. I've also applied the forma to reflect the coming (as of 11-20) change to have a max rank of 40 instead of 30. I've skipped most melee-based mods with the exception of attack speed, because when I actually use 'the arm', it'd be nice to be faster.

Still has less EHP than my Umbral [Grendel], lol.

EDIT as of Operation Orphix Venom
Once I can get the new mods, I'll be replacing [Fury] with [Rage], and (Engine) Efficiency with Repair. I may replace [Continuity] with [Enemy Sense]. Haven't decided yet. [Continuity] has an impact on Guard Mode. Radar may be more valuable than the 4's drain efficiency. To add [Rage] and Repair, I'll have to add a Vazarin forma (for Repair) and maybe a V forma for Rage.
(Now changed with this new version)

Previous version here: https://overframe.gg/build/edit/106291

Later Notes After Completing Build
This mech is now very fun to play. All of the forma's in there, and I've got all of the mods in there except for Thrusters, which I still need to obtain. [Necramech Repair] is a lifesaver for [Voidrig], because there's no reliable way to heal it. It'll give you some breathing room if you screw up with your Storm Shroud and start getting shredded. [Rage] now gives you the ability to get another Storm Shroud when you're out of energy.

[Voidrig] is now much more survivable, as opposed to before when I'd take it to Orb Vallis to rank up and having it be destroyed eventually was inevitable. Still, it's nowhere near as tanky and survivable as Bone Widow, which is also pretty great with a full build.
(My Bone Widow build is here: https://overframe.gg/build/114559 )

With Voidrig, I can fairly easily farm Orphix Venom with the use of a Fluctus for shooting Resonators through walls/ceilings/floors, and pulling out the Arquebex to deal with groups or directly attack the Orphix eye (My RIDICULOUS DPS Arquebex build here: https://overframe.gg/build/104093 ).

Bone Widow vs VoidRig

When you're looking at Bone Widow vs VoidRig, think of it like this:

• Bone Widow is a lot of fun. Melee is fun. The Meathook is cool, and it's really fun trying to single out a Nullifier ([Revenge]!), a Nox, or a larger sentient to skewer. It's also fun with [Voidrig] to quickly pull out your [Arquebex] and blow everything away, seeing lots of colorful numbers, over 2 million even. So, what's more fun? Melee or gun stuff?
• Bone Widow is more simple of a playstyle. He's easier to survive with, doesn't require so much attention to keeping his powers up. VoidRig will totally melt without having Storm Shroud active, and that requires more special attention to maintain.
• Even though Bone Widow can really tear shit up with his [Exalted Blade] and a good [Ironbride] build, the damage you deal is nowhere near [Voidrig] with a good Arquebex build. VoidRig's damage potential is stellar. My Arquebex build has a burst DPS of freaking 5 million.
• So, Tenno, if you can only choose one, do you want the gun or the blade? Squishy or tanky? Consistent or STUPID-HIGH damage? Inaros or Mesa?

My Builds for Reference:
Bone Widow: https://overframe.gg/build/114559
Ironbride: https://overframe.gg/build/115213
VoidRig: https://overframe.gg/build/113615
Arquebex: https://overframe.gg/build/104093