(These are all theory votes, but I feel they're pretty damn well thought out)
All 3 monkeys for Bottom. Now that you're no longer given one for free, it's a nightmare to actually be able to find one of these fuckers, let alone get them to have a usable nature. They're also all sorely outclassed from the get-go by alternative options at this point due to their terrible stats in their pre-evolved forms, as well as the presence of good Grass types RIGHT WHERE YOU GET THEM (Roselia and Petilil particularly, hell even Swadloon would be a better pick than Pansage). The only real plus to having them is that they come with Flame Burst/Scald/Seed Bomb, so you can evolve them right away, but really they're not worth the effort at ALL. Panpour's the best of a bad bunch, but imo still isn't worth it.
Zubat for Mid (Lower-Mid if you get a Mid split again). This may seem surprising, but I'd argue Zubat's not really that terrible. You get a powerful Wing Attack as soon as you get it as well as a Gym for it to solo for free (except Dwebble), at which point it'll likely evolve into Golbat, which at that point is a pretty damn good 'Mon. You have Venoshock for immediate Poison coverage which although not amazing can still get the job done, and although you suck VS. Elesa, Clay is another free victory. Early Acrobatics (Level 33, right after Clay pretty much) also helps make up later on, and friendship evolution can easily be manipulated to your own ends to get a Crobat aroundabout the late 20s-early 30s. When it evolves you also get far better move access, including Cross Poison and X-Scissor, as well as Giga Drain and Heat Wave via Move Tutor if you really want to, although the latter 2 don't come till Seigaiha. It's not amazingly effective against most of the strong trainers afterwards (I'd say it particularly struggles VS. the many Plasma Poison types) and isn't quite as strong as you'd want it to be, but it's pretty damn well rounded (especially as Crobat), and I'm not exactly arguing it for Top tier, just Mid, which I feel it fits the bill for.
Braviary for High. I'd expect this thing is an absolute BEAST early on thanks to its sheer strength, and it even has a fair degree of bulk thanks to 100/75/75 defenses, which though not amazing definitely allow it to take a hit, maybe even 2 sometimes. You can level it up a little bit so it gets Slash (or you could eventually teach it Return), at which point you're ready to go to town on a lot of things. You could even make a case for it beating most of Nimbasa Gym despite the weakness, thanks to its power and a little bit of bulk, although Elesa is another story due to Volt Switch. You can plough through a lot of areas in the game thanks to its sheer strength, and when you get to Yamaji Town you can tutor it Superpower early on to give it some coverage beyond mono-Flying. It's biggest problems imo are its mediocre speed (not so much early but definitely shows later on) and that it doesn't really learn too many powerful moves, it doesn't get Brave Bird unless you grind severely, leaving its best Flying move as Fly, but seeing how powerful it is, and how you get this beast of a mon only right after Burgh, I'd say it definitely warrants High. DESTROYS mid-game, but later on falters only a teeny bit.
Sandshrew for Low. Gets a free gym (save Emolgas) to gain experience, has pretty damn high Physical stats, and the pretty powerful (albeit unreliable) Magnitude at level 17. So why Low? Simple, awful offensive movepool, KOed by most Special attacks, and pretty damn slow, meaning you'll take a lot of hits and if it's against the wrong thing, you're weakened, if not dead. Also does barely anything against the major trainers of the game. Does pretty good against Plasma though, albeit only if you get Rock Slide from Mistralton Cave, otherwise I'd say it's bad, but not without its minor uses.
Combee for Bottom. It's fucking Combee, you have to work to find one that can EVOLVE, and Vespiquen's pretty awful as well thanks to its awful typing and even worse movepool. I don't think this needs much more explanation.
Karrablast for Bottom. This thing did admittedly get helped a little bit thanks to Shelmet being far earlier, as well as getting a Bug Bite tutor to help give it STAB (although it is bad), but it still lacks a movepool, is still shockingly slow, and none of its other problems were fixed whatsoever. Gets SLIGHTLY better later on as it gains X-Scissor instead of Bug Bite in addition to Iron Head, but it gets NO moves to use its great typing and attack with, which is quite depressing.
Nosepass for Low. You may think I'm trolling by not putting it in outright Bottom, but funnily enough, this thing does have its (rather niche) uses. You can evolve it into Probopass immediately by killing a bunch of Joltik or something and then you gain the AMAZING for in-game Steel type to work with. It pairs up incredibly well VS. 2 of the 3 gyms it faces (although watch out for Swanna and Flygon), and can almost solo both of them. It's incredible bulk and Steel typing ensures that unless it's hit by a 4X super-effective move, it's not gonna be knocked out easily, and you can remedy that further by getting one with Sturdy so it can least do something to those foes. It lacks offense and Speed sure, but it could do surprisingly well considering all these factors. It also gains Earth Power and Discharge not too later on, so it can actually easily beat the Plasma goons plaguing you. Not absolutely godly, but not total garbage either.
May have more coming up tomorrow, if any opinions differ please don't hesitate to argue your case. :)