Priority to high-occupancy FCs. I believe what could be done ED relatively quick is to give priority to FCs with N+ Commanders docked (not ships, but Commanders!). This way Squadrons, Expeditions and real Bubble-Coloina-Bubble "weekly train" FCs will be traveling even faster than before.
IMHO, situation is very similar to traffic jams on highway(s) in RL. And solving it by widening highway is not very common in RL. It is rather done by encouraging people using public transport and by grouping more people in one car to decrease the load on highways. Many years ago in Massachusetts I was amazed how huge vehicle moves concrete blocks to take one line from opposite direction and add car-pull (high-occupancy) line to jammed direction. Only cars with 2(?)+ people was allowed on that line.