Peter,
CAveseeker7 is right, and I will not even pretend to know more than him. But, I will write a little bit more of a description as to why your idea isn't practical, and maybe you can get a better idea of your options.
The reason that Closed Circuit Rebreathers (such as the evolution) don't produce bubbles (most of the time) is that they are injecting pure oxygen into the breathing gas as your body uses it up - in essence "re-enriching" a small amount of "air" that you continuously breathe in and out. The CO2 produced by your body is removed from that "air" (more properly "gas") by trapping it in a chemical (scrubber) canister, so no bubbles are created in getting rid of CO2, either.
So, lets assume that you tried using Nitrox in both of the evolution rebreather's tanks. The first tank (diluent) is sometimes filled with nitrox... no problem there. When you begin breathing, the diluent tank is used to fill up the "breathing loop" (diver-to-scrubber-to-02 injector-to-diver) with nitrox and you begin breathing it.
As you descend, the breathing loop becomes compressed and loses volume just like air in your BC. Diluent (Nitrox in your case) is added to keep the breathing loop at a comfortable, breathable volume. (incidentally, this is why you would want a relatively low O2 nitrox for diluent. Because descending demands addition of diluent, so you could possibly end up adding too much oxygen to the loop - causing O2 levels to become toxic. No matter how smart the rebreather's computer might be, it can't add any low-O2 diluent if there isn't any onboard!)
Now at depth, you are breathing the loop and metabolizing the oxygen out of the nitrox breathing loop. The evolution's computer sees this, and triggers additions from its oxygen tank whenever needed. When you remain at a constant depth, diluent is not normally added, because oxygen is added as our body uses it. The loop volume remains almost perfectly constant.
BUT if the evolution thought it was injecting oxygen - which was in fact replaced with nitrox (let's say 40% O2 nitrox) it would have to inject more than 2.5 times as much gas to keep the loop O2 level up. Assuming that the computer didn't freak out from some safety feature (evo users might know) then the inert nitrogen being injected into the breathing loop along with the oxygen would cause the loop to expand, and you would need to dump some volume from it quite often. What you have done is created a very expensive Semi-Closed rebreather - with a seriously annoyed computer to boot!
If you want to dive nitrox and reduce the bubbles a lot, look into the semi-closed rebreathers. They use nitrox, and just let a little bit of it pass out of the loop as yo go along. They reduce the bubbles by 80 - 90% compared to open circuit scuba, and those bubbles come from behind you. They are also cheaper, and in many cases much simpler.
Search these forums for:
Draeger Dolphin
Azimuth (formerly Mares Azimuth)
RB80
