After much consideration I'm going to have to say Dooku wins this. This type of fight would be very unorthodox and it is extremely hard to determine how it would work in reality or who the winner would be, but I believe that Dooku has many qualities that make it seem very probable that he would be the victor.
Firstly his swordsmanship would help him a lot in this fight.
He has displayed incredible ease with dealing with multiple opponents (and not amateurs like Kolar or Tinn (well not general amateurs but amateurs compared to Anakin and Obi-Wan), but Anakin and Obi-Wan - two of the order's finest swordsmen) and I believe that this is due to his experience with a saber and his refinement of Makashi. The point being, his ease and competence with dealing with multiple opponents would be a great asset for him with this type of unorthodox fight with multiple opponents. The fact that Mace was so incompetent with working with his 3 jedi masters to apprehend Sidious also leads me to believe that he would not be competent with multiple combatants period, whether they are on his side or whether he is against them. Yoda and Sidious are both Ataru masters, and Ataru is generally known for being weak against multiple opponents (KOTOR2 backs this up).
The fact that Dooku only needs to wield his saber with one hand while he duels makes it easier for him to pull off a force power while dueling and I think that this would also greatly benefit him in the fight. I mean it is already an unorthodox and strange fight for all of the combatants so why not make it harder for his opponents by combining his saber dueling with force powers. And we have all seen him display the mastery and control of the force that is needed to carry this out competently.
My final point is that every single one of these combatants are pretty close on terms of power levels (and Dooku is arguably the best saber dueler out of the bunch and the 3rd best force user), and that any fight involving these four force users would be incredible and last quite a bit of time whether it involves just 2 of them or tag teams or whatever. But when you make the fight more complicated and foreign to the combatants like this fight, the fight would probably last even longer and because of these points I would think that fatigue would play a huge factor on the result of this fight, and Dooku’s use of Makashi enables him to use up the least amount of energy as possible, whereas Sidious and Yoda’s Ataru means that they use up too much energy (especially Yoda considering the degree to which he uses the force to augment his physical attributes. And Mace is probably the most likely out of all four of them to slip up and die before fatigue becomes a deciding variable (his defence is his weak point and DEFENCE is probably THE most important quality in this type of fight). Because of these points, I say Dooku takes it.