So much for there being too much to list. You can't do it unless you have lots of money to pay for some VERY one off custom work or you can do that very custom work yourself. If you have to ask if it can be done, the answer to these is pretty apparent. This isn't me being a dick. This is me being obvious. So let's take the time to explain it anyways.

First off you have 2 eccentric shafts at your disposal. They are machined. Each of them is 1 piece. For a 3 rotor engine you need lobes that are 120 degrees off from each other, not 180 degrees. This means you will need an entirely new eccentric shaft and can't use the ones you have. You might be able to machine each one you have into parts of another shaft but even then you don't have enough parts to finish the job.

You need an extra housing that doesn't exist that has the intake and exhaust ports for 2 rotors in it. This would require you to custom build one and no one has ever done that yet. One person has adapted a 20B eccentric shaft and modified an existing center housing to work in this place but the center rotor could not breathe as good as the outers due to the size of the ports. You would also have a different amount of intake ports on the center rotor unless you used a 4 port motor and even then it's not going to have the same port timing. I'd prefer not to get into this as well but trust me, it won't work.

You will need to custom make an intake manifold which is actually the least of your worries if you are content on losing lots of the benefit of the current design. You'll lose the VDI and auxiliary port functionality unless you do something really really trick. I'm not going to call this one impossible but rather highly highly improbable. Improbable to the point that we'll see a rotary climb Mt. Everest before it happens. But it's possible!

How do you plan to control the engine? The stock ecu isn't going to do it and one that does will be a couple of thousand dollars and require tuning from scratch. This isn't that abnormal since lots of people use standalone ecu's but it is a pain.

Cooling for both oil and water. Are you going to rely on the stock cooling system to handle 50% more load?

The exhaust. Prepared to replace the whole thing? Not unusual either but still more money to spend.

Even if you get all of this figured out, how are you going to balance the engine internally?

Just paying for all of the components without even doing the engine work itself will cost you several thousand dollars. A swap with a standard already existing 20B 3 rotor is a $20K plus affair and usually far more. Custom building a 3 rotor Renesis will at best double that and then there are costs that you won't ever expect.

Basically what I'm getting at is that a big pile of parts does not an engine make. A big pile of money on the other hand has a better chance. How much money do you have? Unless you can buy a Ferrari today, you probably don't have enough. That's a pretty direct statement but a very true one.