It's way too harsh to force mappers to make equal amount of diffs and even let them be at the same level, and it is another way to encourage perfunctory - to tell mappers to modify their normal into another form of normal.
And you are asking mappers to make insane on their undesired key amount?!
Besides, mappers would just split their maps into 2 sets, or giving up making multi-key maps, making this rule useless at all.
My opinion is only adding "Each key amount must have at least 2 difficulties and one of them must be Easy/Normal.". That would be far more reasonable and deprive privileges that only one diff exists on one key amount being ranked in any circumstances.
And you are asking mappers to make insane on their undesired key amount?!
Besides, mappers would just split their maps into 2 sets, or giving up making multi-key maps, making this rule useless at all.
My opinion is only adding "Each key amount must have at least 2 difficulties and one of them must be Easy/Normal.". That would be far more reasonable and deprive privileges that only one diff exists on one key amount being ranked in any circumstances.