Just don't force me to figure out what it would look like at Legendary rank, you silly people.
You say that but that just makes it sound like a challenge. (Even if putting actual effort into doing things 'stylishly' would be wildly ooc for Nemo)
[ ]Lamenting Cero. Nemo's Cero has always had a peculiar gray color, wisp-like look and strange sound, but this effect actually turns this into a meaningful combat advantage. When the energy of your Cero scatters after firing, it creates phantomatic vision, smoke- or mist-like, just figurative enough to imagine real shapes in them, as well as a distorted, mournful chorus in the area of firing. This allows you to use your own Cero as a smokescreen, concealing your movement in the visions and drowning your sounds in the weeping.
Useful, and compliments our stealth focus
[ ]Devouring Cero. Hunger is scarred into Nemo's psyche, and in some ways she may be able to tap into its dreadful memory. Your Cero can now draw upon lingering spiritual energy in the area in which it is fired. The more energy is released in an area (by Cero and Bala attacks, by Resurreccions, by spectacular flares of reiatsu, by shinigami's Kido, and suchlike), the more powerful your Cero becomes. This is only a slight increase when firing normally, but if you actually charge your Cero for longer more energy is drawn, allowing you to fire above your maximum power at no greater cost if you have enough time.
As nice as this
sounds... 'helps going against enemies stronger and faster than you' and 'charge time' do not entirely mix. Given the whole flash-step thing Bleach has going on, telegraphing just doesn't seem wise.
[ ]Living Cero. A Cero is a mindless thing, braced and then thrown into the world to act as it will. With this Trait, however, your mind still has a grasp on a Cero as it is being fired, allowing you to alter it in some ways. You can widen the scope of your attack, reducing its intensity but catching a dodging enemy, or narrow it to focus its power on a target that can't dodge, or expend further energy to maintain its firing for several seconds to utterly scour the object of your ire.
Also useful, to the point I'm not sure which is better vs Lamenting. If we do want to go full sniper this would be a very good pick for the focusing trick.