Yeah, we're wrong. Blender might be your best option.
I'm leaning this way, but I don't really want to have another thing to tinker with.
I have a 70/30 N2/CO2 bottle (kinda beer gas) and a 100% CO2 bottle. The CO2 bottle has a dual pressure regulator on it (and two manifolds for what is 100% CO2 now). What I'm thinking is that I'll use a gas blender for my "normal beer manifold", blending the beer gas and the CO2 for my "normal beer manifold". Then I'll have straight CO2 for my "high carb manifold". Then have the beer gas straight for my stout tap. Ugh.
May have to pull the bottles out of the keezer and make some sort of pass through. I remember seeing a thread about that a month or so ago, and I liked Mark's design, but I can't find it anymore.
I don't think many companies would want to bottle custom blends for a homebrewer, and if they did the price would likely be insane.
I suspect this is actually the reason it 'can't be done', but being the person I am I want to know precisely why.
I'm sure if you had a draft technician out they've helped look at those things, though.
Not sure of total length, but I know she is running up 1 floor and not directly above IIRC from her There's always a project at the Redbird brewery thread in pimp my system. I think she has a pretty unique system that fits her needs and requires special consideration. I don't have the answers she needs but do "think" I remember those facts from that thread
Pretty good memory, Frank! It's about a half a floor (split level home), but otherwise spot on. Link is in my signature.