Sidious was a patient man, but he was a Sith, and Sith, by their very nature, want to be Drunk on the Dark Side. He wanted to take out Jedi, but he quite obviously couldn't show himself to the Jedi just yet. So he reconciled his bloodlust by cloning himself and adding super-cool makeup (i.e. horns, tattoos). If you accept the Expanded Universe as canon, this would be in character, as in the EU, Palpatine created LOTS of clones of himself. As a bonus side effect, the resulting clone would look like a Zabrak, eliminating any human resemblance. Maul also used a double lightsaber, giving further proof that Maul was a Palpatine clone- no sane being would use such a dangerous weapon. But Palpatine/Sidious had his own body,and did not care if another clone died.