You do realize a five-year cushion isn't strictly required, right? You'll just be paying an extra 10% until you get enough seasoned Roth conversions. Depending on your tax bracket now and in retirement,
this could even be a better deal than doing more post-tax saving before retirement. If you're past your number but for this factor, I wouldn't let it hold you back.
What you can do to get yourself on track for the long run: retire now, withdraw year 1 expenses (paying 10% early withdrawal tax), convert year 6 expenses. Next year withdraw year 2 expenses and convert year 7 expenses. After five years you won't have to pay early withdrawal tax anymore.
A variation on the above: put part (maybe half?) of your pre-tax IRA into a separate account and start doing SEPP withdrawals from there. These withdrawals will be free of the 10% early withdrawal tax, but likely not enough to pay all your bills. You'll pull the remainder from the other IRA (paying the 10% tax), and convert a similar amount to Roth so you don't have to pay that tax in year 6. This might be a more appealing option than the above if realizing 2x your spending as income in years 1-5 would put you in a higher tax bracket than you would like. With the SEPP scenario you would realize less income in the early years, at the expense of less withdrawal flexibility until you turn 59½.
This year there's even a special provision if you're affected by covid-19. You'll be able to withdraw $100k free of the early withdrawal tax, optionally spreading the income over three tax years, if any of the following apply:
* You, your spouse, or a dependent get a positive covid-19 test result, or
* You experience adverse financial consequences due to a job loss, reduction in hours, reduction of business income, quarantine, or loss of child care due to covid-19.
More information about this
here.
I personally don't have to worry about this situation as we were able to save more than the tax-deferred limits for several years so we naturally built up quite a cushion in taxable and mega backdoor Roth accounts. We do have an 80/20 stock/bond allocation across all our accounts because, like you, I feel that a 100% stock allocation is a recipe for bad results in a market downturn. So far this has served us well during the pandemic. On the way down we sold shares of our bond funds to pay our bills, and even had to rebalance a few bonds into stocks to keep at our 80/20 ratio. Then on the way back up it looks like we'll be doing some of the opposite. Buy low, sell high.