RE: house bank and....
"The thinking is a very large battery bank can be used for both start and house bank duties "
No problem at all , deep cycle have lower CCA than starts , but with a pile of them it works well.
Even 50% discharged deep cycles will have the ability to start , its only big amps for a short time.
WE use 2x8D for our 6-71 , and normally start on the "house" batt that is in use.
One advantage of starts is they will stop putting out many amps if cranking is too long.
In 5 min the gas will have dissipated , and cranking can resume.
A ton of deep cycles would simply keep the volts up till the starter melts.