OK for your collateral example I think you're misunderstanding the real issue of liquidity.
In our current system there's 2 main issues.
1 collateral rehypothecation, there's more claims on the collateral say mortgages cause bonds have more issues. There's more claims on the dereivarive instruments from the mortgage than the value of the underlying real estate.
2. The value of the underlying is fundamentally a stream of future dollar's. Which is all debt.
The problem isn't that illiquidity is some artificial aberration from the market. Where the price of the distresset asset is wrong.
Its that given the increased risks in the market caused by the shock your assets are actually worth less. The market would clear just fine if prices could adjust.
The reason we can't is that market clearing Price of all the debt based assets would be 0, or very close.
So in your example they actually aren't solvent system wide because as liquidations happen all the leverage which is more than the assets that got liquidated would cascade.
In my example company c can't get a loan and fails because company a couldn't pay their debts.
Your interpretation is that this is a market failure but what it really is that these companies are really actually insolvent at the new cost of capital. They're supposed to fail.
Demand of what would fall?
Demand of. capital increases during liquidity shocks. Demand of real goods and services also unaffected in first order effects.
I literally don't known what you mean