Raichu-A seems like a solid, straightforward upgrade. It's Raichu with slightly more Special, a Psychic type - and with it STAB Psychic - and a nice Speed tier bump. Psychic/Thunderbolt/Surf/Thunder Wave sounds legit.
Muk-A might work (despite its garbo Special) just because it's the only one of the new Dark-types that looks like it stands a chance of doing anything with the cool Psychic immunity. It forces Alakazam out, spams Body Slam, and explodes on something. I wanna say it might actually make decent use of Fire Blast, come to think of it? Muk's Body-Slam-all-day-every-day gameplan and Earthquake weakness makes physical Normals and Goldon the obvious switchins, and if you can get Snorlax or Tauros to switch into a Fire Blast that might be potentially advantageous. Fire Blast's accuracy isn't great, 30% isn't really a magnificent burn rate, and you do risk thawing things... but you're going to attract a lot of Normal-types what run Earthquake, and forcing them to switch into Fire Blast lets you make Muk slightly less of a soft target for them. I think it'd probably be better than Raticate just because Raticate is so damned frail - and while Raticate does have Normal STAB backing its Body Slam, it's still not really scaring much with its 71/40/77 offenses.
Ninetales-A's Fairy typing is functionally worthless - it resists Twineedle and the Dark attacks that don't exist, and it's immune to Dragon Rage - but it might be kinda cute, because it's a fast Ice with good Special. Shame about the movepool, though - Agility might be useful, but your entire Special movepool is Blizzard/Ice Beam. Good stats, cool typing, desperately needs access to workable coverage moves.
Golem is basically strictly worse; it loses its Ice weakness, but it's still not exactly gonna take Blizzards well given its Special stat, and it loses STAB Earthquake, downgrades from an Electric immunity to just a resistance, and gains a 4x Ground weakness in exchange for... a bunch of special attacks it can't use. I was gonna say "at least it gets Thunder Wave" but it actually doesn't. Yeah.
Marowak, Persian, and Sandslash have cool typings that they can't really exploit at all. Exeggutor gets access to Earthquake and a slightly stronger Explosion, but it's even slower and it trades its Psychic type for Dragon, which provides a bunch of redundant resistances, a neutrality to Fire, (which is a nonentity in gen I, outside of hypothetical Alolan Muk spamming weak-ass Fire Blasts whenever it expects something that runs Earthquake to switch in) and a really damaging 4X Ice weakness.
Dugtrio is weird. It loses Speed, but it still has a pretty solid speed tier, and it hits quite a bit harder than vanilla Dugtrio. It's a little bulkier, and Steel gives it a lot of fun resistances, but it's still way too frail. Probably a minor threat, but I can see tech Dugtrio-A in tournament games occasionally giving someone a headache, because it is legitimately sorta scary, but isn't actually good enough to be common enough to be something you think to prepare for. Losing Slash stinks, though.