I knew someone who did this before, can't recall which jets he used though. He said the flow characteristicschanged quite a lot by the addition of helium into the gas.
What is the flow rate of the O2 jet? If it was low enough then it is basically acting as a KISS valve.
I suppose another option is to connect the trimix ONLY to the bypass on the dosage head and oxygen to the O2 jet. As you descend then the bypass will inject trimix into the loop while the O2 jet adds oxygen continuously. What is the point of having a constant flow of trimix? All you need is for the bypass to add trimix enough to maintain loop volume and for the jet to add O2 just like the KISS.
There are a few points that I can see with either system:
I wouldn't dive it without some ppO2 monitoring. At least two cells, I don't think one is adequate for gambling my life on especially on a deco dive.
You need to know the O2 jet flow rate. If it is higher than your metabolic rate then the loop will become hyperoxic. Don't the Draeger jets tend to be quite high?
You have no manual O2 addition. If the ppO2 in the loop starts to drop then there isn't much you can do to maintain it except lots of flushes. I'd imagine this would make deco planning a bit of a nightmare too.
Personally, my own view would be too just add ppO2 monitors and a KISS valve, the Draegers are perfect for it. Like this guy
www.tmishop.com
I suppose it's one of those things that you can't find out about until you try it. Do tell us how you get on.
Best of luck and take care,
Stuart