A new diplomatic relation specifically for AI-controlled nations

I was thinking (and this is just a casual idea) that if you’ve had good relations before with a player and they go offline (e.g if they were a coalition member gone offline or you and them had a mutual share map) then the AI would change their relation to ‘mutual defence.’ for me this would mean if anyone declares war on you or attacks you then the AI will fight the aggressive nation alongside you and send forces to any owned provinces bordering the enemy, until said enemy is destroyed or is at peace. i only suggest this because as soon as n ally goes off then unless someone fights them then they will not do anything to help you apart from let you move troops through them.

what do you think? will it work? probably not