David,
I don't see any reason why your process wouldn't work. Ferricyanide bleach (with bromide) works very well (you should be able to reuse it, too, for better economy!), but AFAIK, it needs either a sulfuric acid stop bath or a sulfite clearing bath, or a VERY long and thorough wash. (And you need proper wash anyway even after sulfuric acid stop or clearing bath.) I haven't tried ferricyanide bleach without proper stop/wash anyway so I don't know how real the risk of forming prussian blue or reacting with residual color development agent is. Apparently it seems to work for you, and that's a good bit of information. Or maybe your 1st fix is doing the thing.
Anyway, I would increase your second fixer time from 30 seconds to at least 2-3 minutes just to make sure all silver halide created by the bleach is removed. This kind of rehal bleach absolutely needs the fixer after it and it needs to go to completion, as the bleach itself only converts the silver to silver halides, not removing them. Silver halides look milky and gradually turn black in light.
Also, I can't see any direct benefits from 1st fix - bleach - 2nd fix procedure (instead of just bleach-then-fix), except for what you say about the possibility of examining the negative and doing skip-bleach processing if the negative for some reason is severely underexposed or the film is seriously out-of-date. The first fix is taking approximately half (or a bit more) of the silver halides and the 2nd fix is taking the rest.
Bleach bypassing does not only cause increased density, contrast and graininess but it also decreases color saturation. This is very simple; when you mix color and B/W images on the top of each other, it is perfectly natural that this happens. However, the effect might not be as pronounced as some expect. IMO, the effect is very clear, still.
(Most of this was probably clear to you anyway but maybe this extra information helps someone else who wants to experiment instead of using the standard process.)
--
Bob,
Blix shouldn't smell "awful", but indeed it has some sulfur and ammonia smell mixed. Maybe the blix you have differs from what I have used, or maybe there's something wrong with it, or maybe you just have more sensitive nose if you find it awful. Anyway, separate bleach and fix IMO smell less, even though they are not completely odorless either. Indeed, blix tends to generate more gas than separate bleach and fix.
Still, when the bleach reacts with the silver in the film, some sulfur smell is generated. Fixer has a slight ammonia smell. Both of these odors are very slight IMO, but I guess they could be bad in a small, unventilated space.