This doesn’t' seem as complicated as you guys are making it out to be. I do understand that you need to be careful to follow the rules and file all appropriate paperwork, but the 72(t) rules seem to be quite flexible and generous.
Let's do an example. Suppose for the next 11 years I save an inflation adjusted $15.5k/year in 401k, $4k/year in Roth, and $20k/year outside of retirement accounts. Suppose also that all accounts do not grow at all, they just keep up with inflation.
I would be 35 with:
401k: 19k (current) + 15.5k * 11 = 189.5k
Roth: 4k (current) + 4k * 12 = 52k
Non Retirement: 0 (current) + 20k * 11 = 220k
Total: 461.5k (in today’s dollars)
with 25 years to live before 59.5 with full access
Based on this calculator http://www.finance.cch.com/sohoApplets/Retire72T.asp
at age 35 with $189.5k in 401k, I could throw off anything between: $3.9k/year (minimum required distribution) or $14.2k/year (fixed amortization with current max allowed reasonable interest rate). And I get to choose the amount, with the only problem being I'm locked into the choice until age 59.5.
I can also take out the $52k that I contributed to the Roth whenever I want. Say I take out $2k/year for 25 years. So each year I could get pretty much any amount I want to up to $16.2k/year from my retirement accounts (with the caveat that I can't change my amounts from year to year easily).
But there's not even any reason to start taking from the retirement accounts. The better strategy is to burn through all $220k of the money outside of the retirement accounts, taking me as close to 60 as possible. Hell, if the non retirement money ran out, I could then drain the $52k of Roth, and only after that start doing 72(t).
It's definitely true that if you had nothing but a 401k things could get tricky, but as it is there seems to be tons of flexibility to me. After running through this math, I'm more convinced than ever that it's reasonable to pretend that retirement accounts are accessible for the purpose of retirement projections.
PS: pf101 after re-reading your comment you do mention the importance of Roth and taxable for flexibility. This is another topic, but I think that even if you plan to retire very early, you still want to max available retirement accounts more than contribute to your taxable accounts (although you definitely want both). The crux of my argument for this is 1) tax advantages and 2) 72(t) seems quite flexible as expounded on above.