I suspect that they will increasingly be debated over time. My own view, given what we know at present, is that in periods of particularly unusual market duress, central banks should be prepared to move beyond the normal scope of operations to provide liquidity against a broad range of assets and over a longer maturity than might normally be considered. There are two provisos.
First, the central bank has to be able to make a reasonable valuation decision about the underlying asset, and take sufficient excess collateral (a “haircut”) to protect its own position. This probably rules out exotic instruments except under the most dire of circumstances.