Split bus panel

This is a GE split bus panel. I have noted several defects (double tapped main lugs/breakers, corrosion etc…) but my question deals with the breaker installation and where they are placed. The double pole breaker on the right is the “main” lighting breaker. I see a total of 8 breakers you have to turn off in order to turn off all the power. This is because of the 5 single pole breakers above this main breaker. Is it allowed to just install handle ties on 4 of the single pole breakers thus cutting down the “hand throws” to 6? I have recommended an electrician to repair the defects in the panel and evaluate the corrosion but am curious what the proper fix is for what I have described.

I this the main?

This is the only electrical panel, yes it is the main panel.

It’s been rearranged, and no longer compliant with the 6 rule. The 120v breakers should moved to the bottom section.

You pose an interesting question. I suspect (but don’t really know) that you could do that. Another alternative is to move a couple of the single pole breakers to the slot that the unused 50A occupies in the bottom section. From a practical perspective, I would not volunteer the specific method of repair.