WTF is bank capital?

The Minneapolis Fed has developed a plan that calls for a 23.5% capital requirement for large banks: 

 We would require banks to fund themselves with equity that would be equal to 23.5 percent of their risk-weighted assets. Risk-weighted assets means there’s a bigger weight that’s put on something, an asset that’s risky, and a lower weight that’s put on something that’s safe, like a Treasury bill.

Scott Sumner dealing with an equity reserve requirement. 

What is equity in the sandbox?  Or, specifically, take GDAX as a 'bank', what is its equity? GDAX takes congestion fees from traders and gives it to GDAX owners.  There is no other capital on account except the exchange software algorithm and some bit error.

But they shut the exchange when the buy to sell exceeds some 7% or so. So, in the sandbox, how  are the congestion fees to be reserved? Does GDAX retain pat of its fees for subsidies to prevent shutdowns?

The current system:
Truly mutual Money Market Funds, that do mark their shares to NAV, solve the age-old liquidity problem of banking.

I take the quote a bit out of context, but money market mutual funds maintain a shareholder pit. When the congestion is not sustainable, the bank share price drops and:

If a sudden rise in interest rates, or even a spontaneous withdrawal of funds, causes share values to fall relative to the promised future payments of the assets, the return to putting money back in will simply rise.

My claim is that the current mutual funds are doing congestion management equivalent to congestion fee. If we had an implied congestion fee contract, then we can have the congestion optimal, in general, without runs. Instead of share value going up or down, congestion fees go up or down. I this case, the bank can maintain a congestion structured queue and trading bots will engage in triple entry accounting, a three color trade.

All traders see the significant history of congestion.  The pit boss is essentially filling index space from three generators, keeping their mutual entropy nearly constant.

My first shot at this, but the regulators will be interested. It is a bit of a difficult problem.