Only in the most inefficient way possible. The 'problem' is banks are limited in what they can do with this money which ends up creating investment bubbles and other market distortions which hurt the economy overall. If you slowly transitioned banks so they could not invest this money over say 100 years the net result would not be harmful.
In the end money is not actual wealth, it's simply a representation of wealth. Anything that turns money into more money needs an intermediary where some cash flow is generated. And those intermediary's are often harmful see in excess like pay day loans.
Um, no. The type of investing you suggest includes the risk of losing the money. This doesn't work with commercial banks because they are insured by the federal government, i.e. the taxpayer. When people put money in the bank they expect it to stay safe. That's why the concept of a bank exists in the first place. If there was the risk of it evaporating due to bad investments, that would basically be more of "privatized gains, socialized losses."
I am saying if your raise that percentage to 11% cash on hand not much changes. Then next year that becomes 12% cash on hand... until banks can no longer lend money.
At no point in this process is physical wealth destroyed only shifting how loans are created.
A world where people don't need loans seems like a pretty good world, honestly. I've been fortunate enough that my parents were able to finance my college education out of their savings, and I rent my apartment because I don't want a big mortgage, and my life is I think better compared to people I know with student loans and mortgages. A world where everyone has the same access to resources that I had is a worthy goal, and if we can fund that by banning loans, seems fine.
I simply feel banks have conflicting goals as they need to be 'good at' customer service and making loans. This creates a lot of poor incentives and economic distortions.