I doubt that the Repbulic allows Dooku to surround Coruscant with his armada.
I think Ternian gave the answer in the Act 1 thread:
Although near defeat, Count Dooku and his Confederacy of Independent Systems have masterminded the capture of Supreme Chancellor Palpatine.
Tho the kidnapping is still a wishywashy situation it becomes quite clear that this attack is a pure act of desperation. The turnout of the war stands and falls with this offense which undoubtly started far away of Coruscant. Either they took the Republic by surprise or they just fought their way to the core worlds in many bloody battles.
This would present a good chance to show GG's warfare abilities.
It is still nutz to let Dooku AND GG board the same ship during such a suicide manouver.