You seem to be under the strange impression that, even if Herman Cain was somehow elected President, any of his bizarre ideas would make it through Congress.
what's bizarre about 9-9-9? it makes the tax code vastly simpler, broadens the tax base, encourages savings, etc, etc, etc. (bit of advice: 9-9-9 is too simple to explain and understand to attempt to muddy the waters by calling it "bizarre")
as far as getting it passed (*IF* he wins), that's going to depend on how large of a majority the GOP has in the Senate and how much of a mandate Cain wins.
And you think something simple can get through both houses unchanged? Think about what the senate will do to Cain's darling, assuming he can get elected.