M Gengar will be banned so forget about it
I have been using Chesnaught in my stall team for a while, the issue is that he compete with Gourgiest for a teamslot as a grass pokemon, which happens to be a rare defensive spin blocker, losing only two resistence of rock and dark which are not really that common(I disregard Stone miss, and you don't really have that much dark pokemon to worry about)
As a spike/roar you compete with Skarmory, which does not have the gimmick weaknesses(you screwes the sludge bomb users though). Certainly the two are quite distinct in a lot of ways, but sharing the weakness of fire does put them on the same line more often than you think
Chest screws some important threat really well so he is likely to be a very viable OU team candidate(I laugh so many times when your opponent watching you littering spikes all around, forced to switch out to only take a roar into his face). However, I doubt Chest will even make UU at the end as it is too niche to be solid
Btw, for any offensive sets ppl better take a look on Broom first before making quick decisions