Thank you very much Zod for your help, u are a boss !!
Anyway, I have to conclude that there is no way to safely/durably override the core of PS or Smarty with PS 1.7 ( in most aspects what they call 'upgrades' sound to many of us like regressions...), and that there is no way too to make the thumbnails and color swatches functional at the same time... Too bad for one platform that is supposed to be open source and e-commerce orientated...
Every day i use PS and get deeper into it, i get more skeptical about it...
Anyway, i've already invested lots of time into it, so i have no choice but to use it with its full bunch of flaws...