That was unexpected synergy. Everyone loves unexpected synergies and and they also makes you look good when it happens. I think that I would like to try to utilize that same kind of strategy to deal with stat damage. That would be anticipated synergy. There is a shade of difference between these approaches so I've included a graphic to illustrate it.
Now I believe that the way to deal with this is to once again leverage the critical chart. I'm going to rework the critical hits and I'm going to remove all the STR damage effects and load it up with additional effects that impact other stats. Critical hits are supposed to be exceptional and there is nothing exceptional about taking STR damage. This was already being done where the Brain Burn had casters loosing 1d6 MIND points or a Disable arm/hand crit did 1d4 STR/DEX which would have to be slowly healed over time. I'm going to have more crits that impair DEX or MIND or even CHA. I'll also try to mix up the poison and disease effects so that they do a little more heterogeneous stat damage. Monster, item and spell damage that impact other stats, like vampires draining CHA or Feebleminded spell dropping the target's MIND to 1, can be managed on a case per basis, there's no need to have a comprehensive list of these since GMs make it their bread and butter imaging new ones. I might comb through and look for improvements to what 's there now however. Lastly I'm going to consider new mechanics that deal with stat loss. As always less is more when it comes to the mechanics.