No need for that assumption. Equities going down is not a problem for reasonable investors. You just buy more for cheaper prices according to your schedule and wait. You still own the % of your companies. It's not worth less just because you can't temporarily sell it. It would be like saying that price of your house is fluctuating from 0 to 500k depending if there is a potential buyer today or not.

Stock market crash is only a big problem for leveraged over commited entities, very small inconvenience for people beyond accumulation phase (as they may need to sell very small % of assets in coming months) and huge opportunity for everyone else.

Stocks crashing is fantastic for a little guy. It's the same with real estate prices and it's the reason entrenched players do everything to prevent it.