This panel, a Cutler Hammer, has a 4/0 alum. feed from an SEU cable in the top. There are several 2pole brkrs. in the top 1/3 of the panel. and there is a 60amp breaker on the left side one up from the bottom. there is a pair of wires (#4 copper)that connect the the breaker to the bottom of the buss bar. I can determine from that this panel has a split buss. The 60a kills the bottom of the panel only. The top portion, doesn’t appear to have a disconnect, but is bonded, and water pipe grounded.
Any sub panels tapped directly off the main lugs? And when you say “several breakers” is it just six 240volt ones?
One other question, what is the wiring of the top right breaker in the photo? It looks like either three wires are going to it or a single 120 volt is directly above it just out of the frame of the photo. The number of breakers will determine the number of hand movements needed to shut down all the power, which as Jim an Larry indicated, is the concern.
I guess I am confusing the definition of a “throw” of the hand. I can assume that you are saying this as grabbing each handle and flipping it. I am saying (and maybe incorrectly) that with the outer portion of my hand I can kill that panel in two throws. I did it at the inspection.
Grounding and bonding should be okay if it is done like a main panel as you say. If it would take more than six “throws” to shut down all the power to the home then it will need one or more of the upper breakers moved to the lower half or a main disconnect installed separately.
It a disconnect does get installed then it(the disconnect) will become the main panel and this will have to be wired as a subpanel: unbonded and the neutrals floating separate from the grounds.