I used to use a heaphone jack splitter to take a passive spit before a two different distortions in parallel, and then have an ABY at the other end. All three sounded fine, even Y when one of the distortions was off, but Y was a bit louder.
If you're going to have a buffered input at the start of each chain, why not just make a jack lead with loads of splits off it, plug each split into a seperate chain, put a volume pedal on the end of each chain and then plug the outs from the volume pedals into a little mixer, or maybe just another jack lead with loads of splits on it. This way you can select each chain with the volume pedal, and level them out if needs be by fine tuning the volume pedals.