This is a build that I am currently testing for [Lavos].
I am leaving arcanes blank because I feel like they are more of a personal preference and he works well with a lot of arcanes. However, I do think that arcane tempo could be fun to try out with [Lavos] if you plan on using the [Cedo], but this is just for fun and might not be the best option.
I think that [Lavos] works really well with the Mecha set, and so I am pairing that with duration to maximize the effectiveness of status effects. In case you weren't aware, [Lavos] has a secret passive ability, where the status effect duration of both his abilities and weapons are directly correlated to ability duration. Because of this, we are able to stack up more status effects on an enemy before they die and proc our mecha mods, and when you pair his abilities with a weapon like the [Cedo], you net positives in every department, as the [Cedo] can proc every base status effect with its alt fire, AND does a stackable 60% extra damage per status effect on target, which you can then combine with [Lavos]'s 4, which does DOUBLE the damage per unique status effect on target. You can see how this all adds up.
With the Mecha mods, you must use a Kubrow as your companion in order for the mod to proc. I would strongly recommend the [Sahasa Kubrow] for this, as their mods are just generally the most useful for you and your team. Make sure that you are also using both Mecha mods on your Kubrow, as this makes the set much more powerful.
The reason that I am maximizing range is so that we can apply status effects to a larger area, and high range allows us to dunk ability efficiency, since the cooldown we get from our 3 will be higher than if we build for efficiency, simply because we are able to hit more enemies with the 3. Also since we are able to take away from efficiency freely for reasons mentioned above, that gives us room to run [Blind Rage] without any downsides.
[Power Drift] as your exilus mod is not a necessity. I have it in the build because it is a personal favorite of mine, as it is just a useful addition to any build with no real downside. But if there is some other exilus mod that you would rather use, by all means go ahead.
I throw in [Natural Talent], because the mod is necessary for his casts to not be a danger to him, especially his 4, which has way too long of a cast time.
Also as a side note, using Helminth abilities with [Lavos] is not recommended, as you lose out on one of your 4 elements for your alchemical element on abilities, which is more of a hit to your damage and utility output than you would think.
As for survivability, between [Lavos]'s base armor stat, and his passive which gives him 10 seconds of status effect immunity after picking up an energy orb, he is quite a tanky frame without any mods. However, if you ever find yourself having difficulty surviving with this build, I would recommend using one extra forma and then slotting a [Vitality] over the [Augur Reach]. This, combined with his high base armor stat and healing from his 1, should be more than enough to make up for a lack of survivability.
Please let me know what you think! Any and all comments are appreciated, I've worked pretty hard on this build and I'm willing to take any suggestions or feedback to improve it. I hope you're all enjoying this new frame as much as I am!