So thoughts on fixing this system?
This may be against forum rules, but I will give it a shot.
Back in the 80s, I used to repair A LOT of these cabinets.
The weak point, BY FAR, is the HF driver. The other problem was the crossover parts falling off of the board they were glued to and breaking the leads.
So "if it were me" and I had to use these cabinets, I would rewire them to be biamped.
This is for a couple of reasons. First is to use a steeper slope on the crossover which would help a little bit in terms of power.
The other big reason for biamping (they are not "naturally biampable) is to be able to put a good limiter on the HF driver alone.
Biamping would remove the crossovers and the parts falling off from the "equation".
This is not great, but I would flip the top cabinets so the horns are closer together. They are still to far apart for proper coupling, but closer than when stacked as shown.
I would try to avoid using the stacks side by side as shown.
I would NOT use cabinets that are not plugged into amplifiers.
The unterminated cabinets will actually cause a "suckout" of the active cabinets.
Of course you might could put some stronger HF drivers in the cabinets. That would help A LOT.
But it depends on "how far" you want to go.