I figure i might as well try to articulate my current thoughts on the current suspect here, as I find it to be a rather interesting case for M-Abomasnow (less so for Sharpedo, but I'll touch upon it). I'm not pretending to talk about the WHOLE picture here, just a snippit, namely the role of steel types in the metagame and how it applies to M-Abomasnow.
I can't help but feel as though the M-Abomasnow suspect is a product of the environment as much as it is the Pokemon. If we look at the predominant offensive threats of the tier, they tend to all follow a certain trend, namely their disdain for the steel types of the tier. As evidence, those of which I am referencing are Tyrantrum, M-Abomasnow, Durant, M-Glalie, Meloetta, Venasaur, kinda Fletchinder, Aerodactyl, etc. Too say that's all the metagame encompasses would be reductionist - all metagames encompass more than a single element, and all these Pokemon have more complicated roles than just 'kill steel (or ground, for some) = win'. But the sum of the parts adds up to make this metagame's health partially dependent on the health of the steel-type component of the metagame. And many of these pokemon lack reliable recovery or have secondary typings that give them different niches but also more varied weaknesses (pursuit trap the bronzong due to the psychic typing, M-Steelix's ground type yields neutrality to ice, grass, weakness to water). In the case of M-Abomasnow, it's clearly one of the most brazen offenders of this - littered throughout this and other threads you hear people mentioning that M-Abomasnow has few checks and almost always the ones mentioned are 'Bronzong' and 'Escavalier' (the consensus/my opinion seems to indicate Registeel's place is predominantly for stall which can afford to have less momentum, it's certainly less crucial to the discussion). But if we compare this to other Pokemon that have limited checks/counters like Houndoom, we still see a large difference (not a perfect example, but bear with me, I think it gets the point across). Many of Houndoom's counters (Diancie, Poliwrath, Blastoise, kinda Seismitoad) don't have reliable recovery (RestTalk doesn't count imo) and could be susceptible to whittling. What's the difference? I mean, Alomomola is one that's significant, but it's also not the ONLY thing holding this back from 'broken'. And there are 'more counters', but all of them with similar exploitable weaknesses.
In my opinion, I think one of the most significance difference is this environment of hostility towards steel types due to the sheer density of threats that want steel types gone. Water types can certainly be pressured, but it's far easier for steel types because one of the best methods to whittle a Pokemon with weak recovery is with something it counters. This is all a result of the fact that the counter switches into the threat, takes say 15-30%, and then can't easily recover this back for Pokemon with weak recovery. If you switch a Sharpedo into a Bronzong on say the Stealth Rock (not something I recommend due to the risk of taking massive damage, but it illustrates the point), the Bronzong effectively takes nothing due to the switch mechanic. This means building teams around, say, two threats that have steel type counters and one or two things that pressure steel types out, you have an effective archetype that takes advantage of the sheer density of Pokemon that can 'chip' the steel type. And it's not like it's easy to maneuver around this by, say, adding another steel, due to the sheer density of threats in the tier (there is a reason that 'role compression' is the new buzzword among experienced players, it's directly related to the the sheer density of threats in the tier and the need to create teams that assign many roles to a single Pokemon). So with this in mind, the characteristics of steel types provide an exploitable weakness for aggressive-balance (bulky offence, I suppose) through hyper offense to exploit. I think this exploitable weakness is contributing to making certain Pokemon overpowered for the metagame - maybe not in singularity, but it's definitely a factor.
How does this directly pertain to M-Abomasnow? Well, when we are saying that M-Abomasnow has 'very few counters' we are being reductionist. It's also a factor of a metagame of which one of the strongest strategies for offense and some of balance is to break down these very Pokemon that counter M-Abomasnow. And since this has been a creeping issue for a while, the metagame has become adept at developing strategies, both active and passive, of doing just this. So ultimately I'm a tad reluctant to place all of the blame on M-Abomasnow when I think the metagame could also balanced by an overall reduction of pressure. Of course, getting rid of M-Abomasnow also reduces the pressure, and in my opinion something has to give to shift the metagame into place. I think 49 made a pretty cool point when he mentioned that M-Abomasnow could pressure M-Steelix as a steel type in a pretty unique fashion. In some ways M-Abomasnow represents an especially unique place in the metagame and I think it'd be a shame to lose that. But if it's broken it's broken, nothing to do about what it could've been.
I suppose my main internal debate has been whether or not M-Abomasnow is the culprit when we've got others (my mind drifts to Durant and Tyrantrum) who operate with similar pressure against their few counters (also consisting of many steels). But I think that they also have bulky grounds and waters as checks/counters that M-Abomasnow does not, and they have more checks in general than M-Abomasnow. They also have speed and pressure hyper offense better, but that's an entirely different monologue, it's not relative to the lens I have chosen. So whilst I am not entirely convinced to my core, I do think that the slab that needs to shift right now is M-Abomasnow, and as such am leaning towards ban. But I can't say that I don't think it's a bit of a shame, and I think there are other ways the metagame could permutate that could incorporate M-Abomasnow. Banning M-Abomasnow I believe to be the one that has the least risk and most likely to alter the metagame favorably - it'd be cool if the pressures on steels were reduced enough to be at a more manageable level, as it could help stabilize the metagame.
I'm a bit exhausted after that wall of text, so I think I'm going to skip on Sharpedo right now, might edit in an opinion later :p. The above monologue on M-Abomasnow in relation to steel types is only one lens with which to view the M-Abomasnow situation, but I think it's an important one and also a fascinating one! I'd love for a critical response or even a rebuttal towards this if somebody is itching to counter my points, but it's totally cool if nobody is up for it. Also, in general I'm curious to hear if there are any anti-ban opinions on M-Abomasnow, there have been a couple but not enough to feel like I've fully respected the other sides' argument.
Also consider this your quarterly reminder that CB Rhyperior is an underrated threat! This always gets brought up every once in a while, but I still hardly see people use it. It's one of those Pokemon that's easy to overlook in the teambuilder due to the tacit assumption that it's countered by Amoonguss, Alomomola, Slowking, etc. because it often functions as a rocker, but with rocks and if possible spikes support it can break through these Pokemon and cause major holes in the opponent's defensive backbone. I recommend Bronzong as one of the most compatible rockers to use with it (hard to find synergistic rockers with an entirely offensive rock/ground type, probably it's biggest weakness is on the teambuilding front). It's a great balance and even stall breaker for teams that struggle with these playstyles. I can expand if necessary, but I think I'm going to leave it at that for now.