Re. tuners.
I can certainly understand essentially wanting a full-on killswitch and so placing it at the end of the chain. It really all depends on what effects you use and how many. Distortion will probably not help the tuner track due to all the harmonics being generated, and anything else extreme like filters, delays, pitch-shifters etc are just going to spaz it out. So on a small board like Gaz's it wouldn't be a problem, switching things off before a tune is easy. On a larger board with weirder effects, I'd want it at the start, then if noise was an issue, a gate at the end.
Si