I feel like aggressive hazards would almost be just...awkward. You have to waste three turns to get something that only lasts temporarily (One to switch-in, one to set it up, and the last to more than likely switch out again to use the Pokémon you want to set-up). At the same time these could almost be (it's such a buzz word but I can't think of anything better) centralizing to the metagame. Almost like they'd be relied upon to set something up. Of course you wouldn't NEED to, but it'd be much easier to set up something like Dragonite/Salamence/<insert dragon here> with Charcoal up, as their best counters are Steel types. If something is losing 50 percent of it's health switching in (assuming it's just 2x super effective) WITHOUT taking other hazards into affect just seems overpowered as heck. I mean the self-diminishing concept seems like a good way to balance it out, but after the first initial switch-in it's not going to matter much.
To even beat that you would almost have to run ridiculous sets. Scarf Starmie would resist both examples you gave and be able to Rapid Spin them (assuming they're able to be spun away) or outspeed them and hopefully KO them with Ice Beam (Just using the example I gave), or maybe Scarf Gengar with HP Ice (Again, assuming Levitate bypasses them), but even then you're forced to run something with a Scarf to either KO or knock away the hazards, not both. Just seems overpowered to me.
However, on moves that could inflict status upon yourself after using them, I can see that as viable, but unless that thing has Guts or Toxic Heal or something it's almost useless.
To even beat that you would almost have to run ridiculous sets. Scarf Starmie would resist both examples you gave and be able to Rapid Spin them (assuming they're able to be spun away) or outspeed them and hopefully KO them with Ice Beam (Just using the example I gave), or maybe Scarf Gengar with HP Ice (Again, assuming Levitate bypasses them), but even then you're forced to run something with a Scarf to either KO or knock away the hazards, not both. Just seems overpowered to me.
However, on moves that could inflict status upon yourself after using them, I can see that as viable, but unless that thing has Guts or Toxic Heal or something it's almost useless.