First of all, thank you for all these answers, wow !
I’m going to analyse this and think about it; I’m well aware that Kicad is not necessarily the best suited for what I want to do with the turret boards
To answer some questions: yes, I like turrets for the ease of changing a component (prototyping, maintenance etc) without having to remove the whole PCB ; yes, I need copper tracks because there are wires between some turrets :
I usually draw my layouts with MS Visio (and therefore, there is no automatic DRC type verification), so I could “draw” with pcbnew the tracks and make my own footprints (and turn DRC off 
) ; or cheat with very small pads which will be covered by the base of a turret (OK, this is weird )
In any case, thank you very much and I still have to think about whether I should abandon my idea or come up with an acceptable compromise, I’ll let you know