Or just make a brand new Biome for it, common remember that anvil patch making biome modifications feasible? Also Mycellium (Which allows Mushrooms to grow in daylight) != Pollution.
im thinking how much extra work do we want to put the devs threw. i still think a biome where the only form of life is mutated mushrooms = pollution(it also makes mooshrooms less magical) but if there was a new biome lets see how it could be done with out adding blocksim going to list off some posibilities nvm forgot what i was going to say
1.nothing would grow naturally and no friendly mobs would spawn thats a given.(part where roommate starts oil fire be right back)crisis over before it started carry on