So I would first need to switch to fully funding a Roth TSP, then at retirement (and a 5 year cool off period while I continue to work) I could rollover the Roth TSP to a Roth IRA and start drawing on it? I would then continue the ladder, but with my now-freed-up Traditional TSP to a Roth IRA, paying taxes on that conversion and planning to draw on those funds in an additional 5 years.
Basically, but there's no 5 year cooling off for contributions.
It's not my preference to contribute to a taxable account - I'm just trying to understand what path actually gives me access, without a penalty (or minimizes the penalty), at age 47-ish.
Not knowing what you spend and save each year [or what the 'other assets' are in your OP] - but if it's close to $30k (including taxes!), you can do the following:
(age 43) 2025 - $23k to Roth TSP, $7k to Roth IRA
(age 44) 2026 - $23k to Roth TSP, $7k to Roth IRA
(age 45) 2027 - $23k to Roth TSP, $7k to Roth IRA
(age 46) 2028 - $23k to Roth TSP, $7k to Roth IRA
(age 47) 2029 - $23k to Roth TSP, $7k to Roth IRA, Retire, roll TSP to Trad and Roth IRAs
(age 48) 2030 - Live on $30k Roth contributions, convert $30k Trad to Roth
(age 49) 2031 - Live on $30k Roth contributions, convert $30k Trad to Roth
(age 50) 2032 - Live on $30k Roth contributions, convert $30k Trad to Roth
(age 51) 2033 - Live on $30k Roth contributions, convert $30k Trad to Roth
(age 52) 2034 - Live on $30k Roth contributions, convert $30k Trad to Roth
(age 53) 2035 - Live on $30k Roth conversion, convert $30k Trad to Roth
(age 54) 2036 - Live on $30k Roth conversion, convert $30k Trad to Roth
(age 55) 2037 - Live on $30k Roth conversion
(age 56) 2038 - Live on $30k Roth conversion
(age 57) 2039 - Live on $30k Roth conversion
(age 58) 2040 - Live on $30k Roth conversion
(age 59) 2041 - Live on $30k Roth conversion
(age 59.5) - regular access to retirement funds
I think I counted the contributions and conversions correctly, but apologies for any typos. There is probably some more exact timing you can play with to minimize taxes, but that's the basic idea.
Have you read this post about the Roth pipeline?
https://forum.mrmoneymustache.com/taxes/how-to-withdraw-funds-from-your-ira-and-401k-without-penalty-before-age-59-5/