From what I have seen, Nimble Mongoose is definitely not something I want to cut. I'm not sure if I want to cut my Orbs; there's a decent amount of Swords + Snapcaster decks still. There is a lot of Storm, so room should likely be made for sideboard Null Rod. Grixis appears to be the second most common deck; so I'm not opposed to playing all creatures that don't die to Bolt. I have not played against Decay and Push a lot, maybe Tarmogoyf is reasonable. Elves seems to be common, but I have only faced it once in 7 leagues, whereas others have report a bigger presence. Maybe you want sweepers vs. them, maybe LoamPit is good enough. If Maverick is making a comeback, I want Submerges again. Adding an extra removal spell to the maindeck is not unreasonable (7 total, maybe also LoamRing).

(I have not played Canadian yet in this format because it's not proactive enough to play at this point.)