Since the Noveau will suddenly give brush a couple of range options, I'd definitely consider swapping out Special Duration and Swim Speed with some combination of Special Charge Up / Ink Recovery / Bomb Distance. I'd be concerned with abandoning Damage Up due to its crazy team wipe power (
as my short clip above demonstrated), unless I changed my play strategy to mostly avoid melee engagements (which might be a valid tactic, but hard to say yet).
As for Cold Blooded, the problem you must solve with the brush is this (I'll emphasize certain parts due to my strong opinions on the matter):
Being echolocated is a sizable disadvantage no matter what weapon you play, but when your entire existence revolves around ninja-level sneak and swatting enemies in the back,
echolocator makes you utterly useless for at least 12.5 seconds (assuming the owner of the echolocator has no Duration Up perks). And especially at S-rank level, if you're forced to retreat and cower behind cover, 12.5 seconds is an eternity. It's not much better than dying. In fact, it's even
worse than dying if you manage to survive for more than 3 seconds, and then get splatted anyway due to a sniper knowing precisely where you are.
Anyway, you can certainly get away with not running Cold Blooded in certain scenarios. You can sometimes play for a whole afternoon seeing echolocator just a handful of times. But eventually you run into a team with two echolocators on it, who can trade off specials with maybe 30 seconds of downtime in between, and since a well-timed echolocator
effectively wipes your team of short-range members (whether they actually die or not), it will cost you the game.
Just look at the number of S and S+ players running Cold Blooded now, as far as I can tell it's every bit a part of the current meta as Defense Up or .96 Gal.