Never thought about shifting systems as part of a boutique approach! When you say you might want 6-speed, do you mean 1 chainring in the front and 6 sprockets in the back? What's in your vision of the most interesting shifting setup? Do you want to stay with the current spacing of the frame (probably 126 mm)?
I personally have no problem with cold-setting a frame as long as it's done well and the dropouts are re-aligned to parallel after the spacing is correct.