Some have already closed that exit, banning the storage of cash in their boxes. They want to keep your funds available for negative interest rates and possible bail-ins.
The Oatmeal had a post where he talked about how heavy his $200,000 withdrawal was (that was in 20's).
A little Google searching found: http://www.cockeyed.com/inside/million/million_dollars.html
I think Adam Curry talked about buying actual gold bullion and storing that. Still takes a lot of space and a lot of cost in storage. $100M in gold is over 80,000 oz. Two tons of gold?
https://en.wikipedia.org/wiki/Gold_bar#Standard_bar_weights http://demonocracy.info/infographics/world/gold/gold.html
Me, personally, if I had $100M, I'd buy an island somewhere close to an internet backbone. Real estate is always a good investment!