Hawlucha seems like it has some potential, but it absolutely needs to capitalize on Unburden since its offense is pretty meh for SV OU without a SD boost and any power it can muster (high BP moves, SD, even Adamant Nature).
One thing I will mention for your move suggestions, Tera Blast is unnecessary for Dark Hawlucha coverage, as it has access to Throat Chop which has equal power without the need to Terastalize to be used. I'm not a fan of Fling since it's one-time use and commits you to Unburden Sweeping without having gotten your SD boost in yet (or requiring you survive a turn to SD and THEN Fling for your speed at the expense of your one time Dark Coverage), whereas Support moves mentioned like Encore, Taunt, or the unmentioned Substitute provide Hawlucha more means to disrupt opponents or create openings. The biggest issue is that it has a very hard time breaking certain fat balance staples without being crippled like Dondozo, Gliscor, Defensive Gholdengo, and Alomomola unless you run those moves. Raging Bolt also presents a threat to it with Thunderclap and being able to tank almost any neutral hit from +2 with its standard investment.
Hawlucha's biggest issue is that while strong, it's linear and so dependent on its set-up that your opponent will see it coming a mile away, so you need to create an immense amount of pressure and momentum to get it into a position to make that one chance it gets count.