After experimenting further with the WBs, I'm sorry to admit that 2 CBs with WBs isn't defensively stable against long passes.
To bring back stability without sacrificing the superior offense supplied by the WBs, I moved my WBs back into SB possession, coppied the formation of SBs into "formation A" in the "strategy menu" (by pressing "copy to Formation A"), entered formation A, entered "edit position" and moved the SBs forward into WB position, then I assigned one of the four face buttons to manually activate formation A by the pressing the dedicated face button While holding :R2:. Finally I can activate formation A whenever I cut the ball and start attacking, and turn it off whenever I lose the ball. It aint easy trying to coach football and play it in the same time but the final shape of your team is worth the effort.