As it stands, High Security is a safer place for criminals to be active in. Criminals being able to stay tethered in High Security space should be on a timer similar to what happens with enemies of any nation. Security (CONCORD or Customs Agents) should warp in after a few minutes, and revoke tether access, then giving the standard timer that Security would show up.
This also goes hand in hand with a looter middle man that will loot a wreck, go suspect, dump the loot and have a hauler on standby to grab it with no repercussions. That stolen loot should make anyone who grabs it (innocent or criminal) become suspect until that player docks with the loot.
Edit: Other options that could be considered are Remote Reppers/Cap Emitters do not cause CONCORD aggression if you are in a fleet. Burst ECM could be another, but I think that’s more debatable since Freighter pilots duel with a scout webber for warps, or just be in a fleet (could mean webber scouts need to fit ECM resists).