Sorry for the delayed response

Comments on the assumption that you use the freed-up cash to buy T-bills: this is not a great idea, other than optionality (which isn't nothing).
As mentioned, you could do many things, including diversify etc. T-bill was one possibility.
Am curious - what do you do?

the assumption that you use all your funds for this, rather than just some
That assumption wasn't made.

As for possibly being expensive at time of roll:
The strategy mitigates this by buying long dated puts and rolling way before time decay sets in. If vol is up at time of roll then new puts will certainly be more expensive, but your existing puts will also be more valuable. You can't eliminate time decay, but you can mitigate it such that the existing puts have considerable value at roll time if the new puts happen to be expensive at roll time.

During stretches that the stock does badly, your market-value portfolio balance will sink like a rock.
Not sure I see a rock sinking, the proposal is to buy put protection with part of the 'savings' from using a DITM call (as opposed to being being strictly long stock.) You could do many things with that 'savings', the proposal is to buy good put protection with some of it.
I gave some real numbers in the following post using data as of yesterday. I can't say for sure what would happen in future, but the strategy is set up (i think) to mitigate future nastiness.

When it comes time to roll your calls, there may not be suitable new options available to replace the ones you own ...snip
Agreed, but that's always an assumed risk when doing something like this. It's good to state it however.