Nourish is an interesting choice for Koumei due to how well she can supposedly energy tank with Omamori. Naturally high armour and decent health means she gets good Rage conversions and particularly high energy efficiency for Quick Thinking. Her good energy economy means she's not drawing from her energy pool much either.
I say supposedly because I couldn't really make an energy tank build fit with my build goals so I gave up. Something to experiment with at any rate.
Nourish isn’t the MOST boring choice, but it’s near the bottom for excitement.
(Roar and Eclipse are tied for most boring.)
More interesting and possibly good on her:
Wrathful Advance
Coil Horizon
Condemn
Ensnare
Fire Blast
Larva
Silence
I happily admit that I can dismiss Nourish in part because I have Archon Flow. Which is all the energy buffing I find I need.
I also find doing the challenges for decrees disruptive to game play and in many cases, achieving the mission objectives. Sometimes for entire rounds of defense! Worse, you can then end up with a decree that offers nothing to the current mission.
If we got a 5 panel choice of decrees as in Duviri, that would fix some of the bad that is the current Omikuji.
Alternative title: I turned Koumei into every other frame.
If you're going to get rid of the crux of her kit, really just play another frame. Of course to each their own, but I'm tired of seeing people complain about Koumei when they haven't really given her the chance and used her in a way she'll shine.
It's like when Tenet Glaxion came out and everyone tried to make it into Torid Incarnon. Surprised Pikachu face.
I tried to like her 2 ability I really did, but doing random mini games to get a buff is not my thing, as for nourish I pair it with energy nexus and get my energy back instantly without needing arcane energize, thats why I use nourish personally... I will experiment with more builds for her, maybe I'll give her 2 a chance...
Personally I did not need to put anything into energy for Koumei besides Equilibrium and Synth Deconstruct.
I am very much a "use the right tool for the right job" type player, and your Warframes are tools just as much as your weapons are. Of course you mix the fun in there, but the point is to not make a Warframe into something they're not and expect efficiency and effectiveness.
As someone in this post already said, Koumei is a probability/statistics frame at her core. She has a ramp up period with each mission, and so in order to almost guarantee effectiveness, the biggest resource you have is time. In other words, she is not going to be effective in short missions. The other big resource you have is your arsenal i.e. the tools you can control going in. The trick is to maximize that by using tools and mods that will mostly give you stats that you know will not be provided by decrees.
So most notably that means not focusing too much on ability strength and efficiency in your arsenal, and instead focusing on interactions that can proc off of the decree effects, or flat modifiers for stats that won't be touched by decrees such as range and duration.
And the last thing is to accept that your run might suck for the first 30 or so minutes. By around 30-40 minutes, based on probability, your run should start to settle in and you'll see the pay-off of the decrees.
I have not personally subsumed any abilities yet, but the candidates would be her 3 primarily, and potentially also her 1. Omamori isn't very useful in its current state considering it doesn't actually prevent you from dying, and more or less is worthless beyond the small window between not needing damage mitigation and being prone to one-shot damage. Kumihimo is also fairly redundant in the context of her 4, and can be removed if you have no real need for diet Bunraku.