My issue with this every single time that this subject is brought up is
1) Chansey is an OU pokemon. Not Uber. It is on level with Gliscor, Clefable, and quite a few normally used pokemon.
If you wish to find ways to beat this pokemon its actually really easy "The removal of Eviolite is a big problem for Chansey, severely diminishing its bulk, which makes it far tougher for it to handle many of the offensive threats that it would usually be able to deal with" - Smogon Chansey article SM/OU
2) Blissey is an UU pokemon. Not even to the point of being OU. Aracanine and Crobat are on this Tier. Meaning there are way better options than Blissey.
If you wish to find ways to beat this pokemon "Fighting-types with access to setup moves, such as Cobalion and Heracross, take advantage of Blissey, and Breloom can cripple a teammate with Spore on the switch"
3) For me personally, it always feels like people's immediate reactions whenever they go against a stall team is to post something against Blissey/Chansey on the forums without doing any research on how to beat these mons. I am not saying build your team around them, but every single one of these posts feels like its simply just a salt post with no real thought on what if we did ban it. What would that in turn mean? That would mean you could ban quite a few more things just cause you don't like them. Rain teams because you know the counters but as a team they are annoying to deal with? There is a reason stall teams are "30min to wins, 5 to lose" Yeah, they are annoying, but just cause they are doesn't mean they should be banned.
In summary, this suggestion seems foolish to me. -1