i'd vote no on going a vintage mixte for legitimate touring. even when screwing around town with a modern plastic coke bottle rack on the back of a retro-restored mixte, i've felt significant sway coming from the rear triangle. if you're really interested in doing self-supported touring, i'd suggest you'd go with as much modern stuff as you can, without violating the aesthetic of C&V. for 300 euros, you'd probably be able to buy a sturdier used steel frame, either in drop tube or mens' style. obviously the caveat of 26" > 700c and rim brakes > disc applies.