This has zero to do with concord and only applies to faction police and negative status between -2 and -4.9, before a player hits -5 and is kill on sight anyways. What it would mean is that depending on your concord security status you would get instantly suspect flagged when in a system where faction police would also engage you.
Yes it would make travel through high sec much more difficult for players and yes I would also agree that the response times would have to drop considerably if a LE is applied with a player that would naturally draw faction police response.
Yet atm there really isnt much deterent from faction police as I ahve even seen BS warping around with low sec status or players circumventing faction police to camp in enemy high sec. By having them go suspect it would mean that anyone can defend the factions space from these incursions and truly limit a players involvement in another factions space while being a criminal or enemy to that faction.
Players need to police more and allowing anyone, deputizing citizens into that fight that live in the factions space as god like capsuleers seems to be a good way to get the job done that faction police cant seem to get right.
And Lugh as for your need to go to trade hubs with bad standing would mean you would need to find markets closer to your base of operations and not entertain your criminal endevours or frequent a place where such criminal actions wouldnt have consequences such as high security space.