Dealing with a financial system wipeout might be easier than we think. I know next to nothing about crypto currencies so I will leave that out of my comments. Maybe some others can help with that.
The value of a dollar is vastly less than it used to be. Even fiat paper money and coin could still have value without banks if the majority of people are still willing to use it. One option if "electronic money" is devastated is to revert to cash and coin and maybe even some local currencies such as tokens given by farmers markets. The example I have come up with would be to value a penny (1 cent) as a dollar. In this scenario a nice restaurant lunch formerly costing $10 could be paid for by 10 cents.
Employees probably won't get paid normally if the banks go. However, this could be used to correct massive systemic inequality/injustice. "Employers" (for the time being, provided they are not "corporations" which will totally lose any rights as "persons") can pay "employees"/workers in EQUITY in the business giving the (former) "employees" ownership of the businesses they work for. People with equity will gain a share of profits.
Corporations cease to have rights. Banks cannot own property. (Mortgages would be moot? Possession is 9/10s of the law?) Anyway, the true economy based on human work would be restored, I think. Businesses could still exist but corporations could not. Most people would not work for others as employees but become owners of businesses themselves (farms, retail stores, repair shops). Women's endeavors as "home managers" would become respected again as the domestic economy is the most important of all.
For those who may be Christians, as I am: I think my ideas have been shaped by "words" given to me by God during times of stress. While dealing with extreme financial difficulty I "heard" God tell me "You don't need money, you need the things money buys." It boils down to food, clothing and appropriate shelter. Also, a few years ago, I was trying to offer a service worker a small tip (maybe a dollar) and again I "heard" something along the lines of "That is a lot of money". I think God was showing me that coin and small bills, the "In God we Trust" money would be restored to value.
I hope all who are able will turn to God through His Son Jesus as the efforts of men and demons are futile for our salvation.
Some of the ideas above are "my" ideas. I hope they will inspire thought and new ideas, but I don't claim any special wisdom or insight.