That's a classic Ryco job.
They use bolt-switches, fused, to feed a meter stack with T type fuses for each tenant in a NEMA3R box.
I can't imagine you engineering anything cheaper to rig up.
You may have to purchase a wireway extension box if your service feeders to tenant panels have to go overhead.
Out my way a rehab that complete means that the latest Code must be followed -- no grandfathering.
Biggest bid issue is just how open the project will be -- and what is your bid scope.
If going overhead seriously consider aluminum MC feeders.
Ultimately, re-habs involve extras. THAT'S where you recover from your under-bid.
Good luck.
