Asswipes who want to provoke us with violence cannot be deterred with good reliability by the threat of primitive retaliation. All-too often retaliation is what they want to provoke, after all.
Years ago I proposed a schedule for withdrawal from a war of occupation which featured a deterrence element against violence; the troops would be scheduled to withdraw piecemeal over time, but for every one soldier killed or wounded in action a fixed quantity of soldiers would be sent as reinforcements. Any 'freedom fighters' claiming to fight against occupation would face the dilemma that fighting against occupation would actually prolong or even greatly grow the occupation.
I think something similar could be done against errorists, particularly errorists who are linked to a non-elusive party like daesh:
We could simply pass a law (effective for 10 years) which compels us to send aid to the enemies of the errorists for every of our citizens killed by errorists abroad or anyone killed by errorists in our country.
1,000 small arms with munitions and accessories
100 4wd cars
100 missiles and one missile launcher
10 mortars with a thousand rounds (and more auxiliary charges) each
10 instructors who train the new users for six months
For one severely injured person:
500 small arms with munitions and accessories
50 4wd cars
50 missiles and one missile launcher
5 mortars with a thousand rounds (and more auxiliary charges) each
5 instructors who train the new users for six months
Both would be to be delivered (very publicly) within two months. Stocks would be purchased from other countries if the own stocks would otherwise drop below a defined minimum level for collective defence. Such purchases could be pre-arranged just in case, in order to meet the two-month deadline.
Additionally, the law could include a lump sum delivery as answer for failed every errorist strike.
I suppose we could skip many "counter-terrorism security" expenses and would still be safer than with the status quo policies.