Simisear: I agree with Hex on the Timid Nature. You have Nasty Plot, so you don't need Modest so much. You might also want to run Focus Blast and HP Grass, as there aren't as many heavy Pokemon in NU. However, you can keep Grass Knot to deal with some of the heavier eviolite users and Wailord.
Emolga: I'd run a Flight Gem so that when you want to use Acrobatics at full power, you won't have to first use Spark. I'd go Motor Drive over Static. You aren't wanting to take a hit with Emolga, so I don't think Static is the way to go. Finally, with Iron Tail, you might want to switch it out for Pursuit, Quick attack, or even something like Encore. Iron Tail is mainly for Rock types, who I don't think you'll want to stay in on and hope to have Iron Tail hit. And anyways, even if it does hit, it will be unlikely to KO, seeing as most Rock types you'll be facing will run Eviolite and have a high defense, at least high enough to easily survive Emolga's low Attack.
Basculin and Vanilluxe are good.
Raticate: Reversal is always awesome. You could replace Zen Headbutt for it. Your Facade can handle Poison types better than Zen Headbutt anyways, and Fighting types aren't so much a problem in NU. Nor are Ghost types, the most common one you'll see being Yamask, who you do not want to try to take down with Raticate anyways. Burn on a physical attacker without Guts is something you don't want to deal with. You also might want to have a Speed boosting nature.
Leavanny: Swadloon gets Eviolite. However, it doesn't get any recovery, even the slight recovery of Leftovers. And it won't hit as hard as quickly as Leavanny. And it doesn't get as good an ability. But still, Defense in the 400s and Sp Def in the 300s unboosted is very tempting. You could also just run Grotle and not have that x4 Fire and Flying weakness.