The OP didn't phrase his question very well but it is along the lines of:
You have 100k. Which is better
a) 100k in roth: 50k contributions, 50k of earnings
b) 100k in taxable: 50k of cost basis, 50k of capital gains
If you in the 0% bracket , there is not tax advantage to you for the roth and you don't have to wait til 59 or do a 72(t).
The roth conversion strategy is designed to do 2 things
1) allow you to get the tax deduction on contributions and hopefully not pay income tax on they way out
2) get access to the money before 59 without having to do a 72(t)
Is there a case where you can end up with too much of your assets in retirement funds? I guess but it would be pretty hard. Take a person that had a 1 million dollar portfolio split 800 ira/200 taxable who is sucking out 40k/yr. We will assume 6% rate of return on the tax deferred (lets assume taxable is in like tips) and 2% inflation. In 30 years you will still have 617k in your ira (+ ~889k in the roth). Now sequencing will change that exact ratio.
In the worst case were you coming up short, start 72(t)ing out some more money. If you need more than that, I think your in trouble financially:)
I'll just have to run a spreadsheet comparison, and of course keep in mind that the interest from the Roth is not actually lost.
That last bit is the point. If you convert to a roth and then withdraw after 5 years the interest will continue to exist, you merely cannot take it out until retirement age without paying the 10% early-withdrawal penalty. If you need the extra $100 a year or whatever it is right this second then simply convert a little more and use the interest when you're 60.
All other things really are equal, so therefor it's best to use the account that has the greater tax advantages. So use a Roth, not a taxable account.