I've built and used many loop switchers and used them to control more than the average amount of pedals. IME if you are worried about noise you may want to focus on your power supply and cable more than anything else. I'm sure there's exceptions to that but... hasn't bit me yet.
ultimately, if all you need is a loop selector and an aby switch... just get that. Plenty of folks building 8 loop control boxes these days and it will keep you from tap dancing and be pretty simple functionally.
http://www.loop-master.com/
http://www.americanloopers.com/
the GCX is nice if you plan to use midi, but I'm fairly certain you can find some threads that will contend whether or not it's actually true bypass.
in fact "use the finest gold relays sealed in nitrogen" pretty much means not true bypass (at least not in the mechanical sense). that said I don't think it takes much away from a great product.
carl martin is said to have some nice buffers
for me, there is nothing out there that will do EXACTLY what I want (order switching, mechanical true bypass, buffer control, tuner out, small size, simplicity)... so DIY!
plenty of info on the net:
http://s2.photobucket.com/user/PRSplaya ... B.png.html
EDIT: as a side note... you mention concern about fx order, and if you are (say) using a germanium fuzz and love the pickup interaction: I think mechanical true bypass is going to yield the best preservation of that dynamic.