oh I really wanna take a shot at this question given that archeops is literally my favorite Pokemon of all time.
to start things off, we'd have to consider what kind of ability archeops would get in return. something amazing like magic guard or protean, or something even worse like truant or slow start? for this scenario, i'm gonna go with something that neither hurts nor helps archeops, like illuminate.
-archeops' offensive stats are incredible, with a massive 140 attack and respectable 112 sp attack, and that's before throwing items into the mix.
-in addition, it actually has a solid movepool to back it up, such as access to knock off, STAB acrobatics, and the coveted edgequake. its special moves are a bit less impressive, with only focus blast really standing out, but it still has the power to make the most of it.
-110 speed outspeeds the majority of ou, and after a single agility or rock polish, it can beat any unboosted Pokemon.
-said speed combined with u-turn means it can act as a very capable choice banded scout.
-access to roost means that it has reliable recovery at the cost of gaining a ground weakness.
-archeops' varied moveset and immense power means it has a favorable matchup against a large amount of the ou meta, though the ones it can't hit super effectively, such as celesteela, are gonna give it some serious issues. which leads up to...
-as a flying type, archeops has a weakness to stealth rock. as a rock type, archeops has a weakness to everything. being immune to ground is useful, but a crippling weakness to steel, rock, electric, ice, and water does not help things.
-65 in both defenses and 75 in hp may be the reason archeops went extinct. while it's able to ohko a ton of Pokemon, anything it doesnt can easily take it out in return. archeops' biggest threats would be tanky builds that can hit it super effectively, aka a large amount of water types.
-priority is a major threat. while tapu lele can temporarily nullify this weakness, if that doesn't work, a weakness to bullet punch, aqua jet, ice shard, and a neutral matchup against mach punch, vacuum wave, and sucker punch means that even a speed-boosted archeops is in danger of being ohko'd before it can wreck havoc.
-i cannot stress this enough: greninja is an unwinnable matchup for archeops. greninja naturally outspeeds archeops and can destroy it with any given water move. even if you've maxed out your speed and have a focus blast ready, greninja still has priority in water shuriken, which means that unless you switch out, you're just giving the opponent a free ash-greninja transformation.
all things considered, I think placing archeops in ou might be giving it a bit too much credit, and I say this, again, as a huge archeops fan. the power creep over the years has done a lot of damage to the metagame, and archeops' impressive stats don't have the same punch anymore. that said, I definitely think it would be a bit much for uu, so I think uubl is where archeops would comfortably roost.