Given your massive taxable 'stache, you are correct that you may not actually need to do a Roth pipeline. But under some circumstances it would be stupid not to. Specifically, assuming you do not have any earned income and will have very simple taxes, you will have a $24K standard deduction available. Any amount that you convert from your IRA/401(k) counts as income. So that means that you can convert $24K every year from your 401(k)s/IRAs into a Roth, and pay zero taxes on that conversion. And of course since you didn't pay taxes on that money at all when you put it in your 401(k)/IRA in the first place, that means you get tax free contributions, growth, and withdrawals on every penny that you convert. That's called a win-win-win.

That said, your situation may be somewhat different given your significant CGs. There is still a 0% tax rate threshold on CGs, but it is based on your AGI + CGs; I think the total for MFJ is around $77K to stay in the 0% bracket. So depending on how much you have in terms of CGs to meet your annual living expenses, it is possible that adding $24K more "income" via Roth conversions could push you out of the 0% CG bracket, which would be costly. Similarly, if you do take a part-time job, that would "take up" some of the $24K space the standard deduction provides. So you should definitely run the numbers and check out how things would play out in your particular situation.