A Fighting STAB, Knock Off, and Poison Jab give it nearly flawless coverage as it is. Niche moves like Leaf Blade and First Impression are nice to have and might see some usage, but their coverage is poor in comparison. Brave Bird could conceivably see some usage as Flying/Fighting is a very powerful type combination, but lacking STAB on it hurts, and it really offers very little in the way of coverage compared to Knock Off/Poison Jab. Rock-type coverage would also be appreciated but isn't necessary for its success.
I think Sirfetch'd's competitive viability hinges on just how much of an improvement its stats get over Farfetch'd. Farfetch'd's problem has never been its movepool, it's pretty much always been its abysmally poor stats and the fact that Pokemon like Talonflame, Staraptor, and, well, nearly every other Flying or Normal type in existence severely outclass it. Sirfetch'd, as a pure Fighting-type, is no longer competing with such Pokemon and the pool of viable Fighting-types it has to compete with is much narrower. I think it's pretty safe to assume Sirfetch'd will receive a boost to its Attack, and considering Farfetch'd was given a pretty decent base 90 Attack in SM (which isn't bad for a non-fully evolved Pokemon, as Farfetch'd now is... I hadn't considered this before, but Farfetch'd is now LC legal, and that could shake things up. I foresee a ban from LC in Farfetch'd's future.) this should put it in a nice position. However, Farfetch'd still has abysmal bulk and low Speed. One of those two factors would need to be patched up upon evolution for Sirfetch'd to really shine.