I'd like to start a discussion again on Charmander to B. I'm going to compare it to squirtle, the posterboy of A rank now that it has been rejected to be S.
(1) Gym matchups: Other than sabrina, charmander performs worse in every major matchup compared to squirtle.
Brock: I didn't use a potion but charmander at lvl 12 has a good chance to lose the matchup between geodude's tackle and onix's bide chip. Squirtle meanwhile solos at lvl 8 meaning you can train your normal types n nidoran on the routes without issue. I won't call this a bad matchup for mander but squirtle is obviously far better here.
Misty: Pretty obvious how wartortle is much better here.
I'd like to state that beating these two gyms r pretty important due to being unskippable unlike later guys like erika and surge.
Lt surge: Both charmeleon and wart loses to raichu but beats the electric. Dig meleon fares better here but dig is a super contested tm. Slight edge given to charmeleon due to the possibility though considering meleon lives a tbolt
Erika: Even with ice beam, wart seems to be a no according to other runmers. But Charmeleon isn't good either due to ember being dog shit. Equal matchup.
Koga: Zard has slash now but due to the poison types' high level and defense, blastoise is better here with surf giving you less opportunities to get exploded by weezing. You can go and fetch fire blast from cinnabar but the route is filled with waters, the levels r high and you need to get surf in fuchsia first so quite the detour to my eyes.
Sabrina: Wow zard is better here for once! I can't remember blastoise's progress but i imagine zard's ability to outspeed and slash past zam gives the dragon an edge here.
Blaine: blastoise is much better but the fire types do not attack zard with normal moves so zard does well too. If the ai can attack, it cannot sweep without a potion due to the damage racking up.
Giovanni: Sweep for blastoise but zard is actually pretty good here due to fire blast's sheer power. Cannot ko anything other than duggy tho so you can't sweep.
Lorelei: zard is terrible here, only beating jynx. I know ppl have said otherwise but i cannot get how blastoise will fail to beat at least slowbro, cloyster and jynx. Dewgong perhaps the ai can go wrong with growl and rest but slowbro has water gun, jynx has thrash and cloyster has supersonic as their best chances when blastoise at least 4koes back. Tedious perhaps but not more tedious as charmander's matchup against brock for sure.
Bruno: Both r equal cuz onix suck. Hell, i even want to give zard an edge here due to being immune to machamp's fissure.
Agatha: Similar matchup but zard has the slight edge due to being faster than haunter, giving it a less chance to get haxed.
Lance: Obviously, blastoise is a lot better here with an ice move, zard can beat the dragonairs and thats it.
Blue: Similar matchup but zard no longer outspeeds zam this time making it an even matchups for both starters. Zard doesn't like rhydon, eggy is more annoying than arcanine and blastoise is annoying to teammates with blizzard but gyarados' threat equalizes the balance enough that blastoise only has a slight edge.
Considering that blastoise has six clearly better boss matchups out of thirteen (brock, misty, blaine, giovanni, lorelei and lance) compared to zard's sabrina, i'd say its fair to differentiate their ranks. But what about route cleaning? Surely, slash will favor charmeleon right? Well,
Early game to brock:Charmander has a clear edge here due to ember meaning it can't get poisoned by pesky weedles.
To misty: Wartortles improved power has made bugs trivial so the matchup is roughly equal except for the rock and grass trainers. Do note that unlike mander, wartortle has mega punch to overpower the grasses.
To surge: wartortle got bubblebeam here making it clearly the better choice in the routes. Mander on the other hand struggles with the fire and water types in S.S. anne. Ember has also start to become an abysmal move, making me recall about a moment when ember failed to 2hko an oddish forcing me to return to the pokemon center to heal the status. This is also why manders advantage over grass types is far less useful than wartortle's edge over rock and ground types, they don't ko and the statuses are nasty.
To erika: Both are mediocre in this period but meleon is far worse due to embers shittiniess, the rock tunnel and the water trainers below lavender town.
To koga: Charmeleon finally gets slash at lvl 33. The things is it doesn't quite hit hard due to charmeleon's low attack and depending on route, it can turn out that you're supposed to hit koffings with slash, leading only to 2koes. But of cuz,slash >>>> bubblebeam so charmeleon finally becomes clearly better. For three levels at least, blastoise instantly gets surf in fuchsia, giving it an equally powerful attack that isn't resisted by rock types and has super effective coverage.
To sabrina: Zard should be overleveled enough that surf being a special move doesn't matter.
To blaine: Same with sabrina,zard too high leveled to matter. If you're passing here early to get the fire blast tm, keep in mind zard doesn't like the abundance of swimmers in both routes to cinnabar. Slash only koes the mooks, not the fully evolved mons (even at like lvl 42) and the routes are filled with these boys.
To elite four: Zard finally gains flamethrower around here and thus becomes slightly better in this period. Though blastoise with blizzard /ice bwam and surf should be roughly equal
So according to the logs, from about lvl 20 to 33, meleon has a dead period terrible enough to mandate dig (which i used btw, i just kept spamming embers to check if digless meleon could survive in this period). Meleons slash advantage is trivial since its only for around three levels and even with slash, its not a route killer, being roughly as strong as kingler's strength. So, you're not killing anything other than mooks and bulkier stuff like marowak can even take two. Compared to squirtle, i'd say charmanders route cleaning is clearly worse with the only superior instances being the brief viridian forest and pre surf period.
Tldr: For a pokemon with six clearly better gym matchups and better route performance, blastoise to me clearly should be a tier above zard.