It seems a bit strange that I read through this whole thread, and there were not too many responding members who were really attempting to grapple how bitcoin fits into this FIRE concept, except perhaps Franky1 had the post that discussed the FIRE idea in light of his bitcoin holdings.

Surely, the main underlying ideas of how FIRE plays out within traditional assets are sufficiently outlined in OP, which largely is that when any of us might decide upon living off of our investments in a passive income kind of a way, our annual withdrawal rate should on average be less than the amount that the various investments are earning, so in that sense on average the investment portfolio is not getting smaller in terms of its dollar value, and if we have 25x our annual income/expenses, then withdrawing 4% per year remains enough to sustain ourselves at that same rate for an indefinite period of time, and presumptively in a perpetual basis.

We still potentially have the problem of calculating real rates versus nominal rates, and surely with ongoing debasement of the dollar we may well find that such a fixed income may well not keep up with how the costs of goods and services continue to rise in prices at a rate that is much greater so that we may well have to suffer from ongoing decreases in our standard of living and/or spending less each year in real terms if we maintain the same flat rate of withdrawal at 4%.  Surely, if we are able to invest in assets that generally appreciate more than 4% per year, then we may well be able to account for the debasement of the dollar by increasing our withdrawal rate in order to account for such ongoing increases in our cost of living.

I personally believe that bitcoin resolves a lot of the issues, yet surely there could be questions and concerns that the FIRE persons might have in regards to how much of their investment portfolio that they might keep in bitcoin as compared with other places that they might hold their assets.  Personally, I don't have any problem with the idea of treating the bitcoin investment differently from any traditional assets that are in place, and so perhaps just continue to withdraw  from traditional assets using the 4 % formula and then withdrawing from bitcoin to supplement such withdrawal and to withdraw from bitcoin last, since bitcoin remains amongst the best, if not the best investment that any of us could have.

There are also possibilities that guys choose to ONLY have bitcoin as their investment and NOT to have other traditional categories of investment, so in that case, the bitcoin holdings would serve as the FIRE asset, and I personally believe that if a guy valuates his BTC properly, by measuring the value of his bitcoin in accordance with the 200-WMA (bottom prices) rather than spot prices (which tend to be all over the place), I personally speculate that retaining investments in bitcoin a person could withdraw up to 10% per year based on the dollar value of the 200-WMA, which largely means that a guy would ONLY have to have 10 years of his expenses/expected annual income in bitcoin so long as he is valuating his BTC holdings at the 200-WMA, and perhaps in engaging in other protective measures, as I describe in my sustainable withdrawal thread, which means engaging in reductions of his withdrawal rate if the BTC spot price goes below 25% above the 200-WMA and other kinds of withdrawal reductions as I describe within the sustainable withdrawal tool guidelines.

For example, look at this:
>>>>>"When the BTC spot price is at least 25% above the 200-week moving average, then at least 1 month's withdrawal will be authorized; however,

A) if the BTC spot price is between 10% and 25% above the 200-week moving average, then you will be authorized to withdraw for only 90% of the current month's limit.
B. if the BTC spot price is between 0% and 10% above the 200-week moving average, then you will be authorized to withdraw for only 85% of the current month's limit.
C. if the BTC spot price is between 0% and 20% below the 200-week moving average, then you will be authorized to withdraw for only 70% of the current month's limit.
D. if the BTC spot price is between 20% and 30% below the 200-week moving average, then you will be authorized to withdraw for only 50% of the current month's limit.
E. if the BTC spot price is greater than 30% and 35% below the 200-week moving average, then you will be authorized to withdraw for only 40% of the current month's limit.
F. if the BTC spot price is greater than 35% below the 200-week moving average, then you will be not be authorized to withdraw any BTC from the budget."<<<<<<

Surely guys can also stick with lower levels of withdrawal of their BTC such as some where between 4-10% (perhaps even at the lower ends of such range), which from my thinking would allow their BTC holdings to continue to grow while they may perhaps decide to defer their actions of withdrawing at something like a 10% annual rate... and yeah, of course, anyone who overly depletes their BTC too soon, ONLY have themselves to blame for failing to figure out a withdrawal system that would end up playing out in sufficiently sustainable ways.