Here's my plan. In order to ease into this process I want to give away more than half of my salary the year after I hit my FIRE number. In my mind, this is mentally equivalent to declaring myself FI and then continuing to work for OMY and splitting my take home pay between charitable giving and building my safety buffer.
I've been thinking about this a lot since your update post.
My (amorphous, undeveloped) plan had always been to get to the retirement finish line ASAP (which necessarily means deferring any charitable giving until
after achieving FIRE, except that I have been making some relatively nominal contributions during my working career), and
then focus on charitable giving in retirement. Because I am, like most of us, in all likelihood grossly oversaving, I expect to have substantial excess over "enough" to give away once it becomes clear that my retirement is on a successful trajectory.
A side benefit of this strategy, I had always assumed, is that it would maximize my net lifetime charitable contributions (because every dollar that I defer giving away now will turn into many multiple real dollars that I can give away later). But this ignores the tax considerations, which I never really focused on.
Your "OMY with half the proceeds going to charity" plan will allow you to take a substantial tax deduction in your final year of high-income employment.
Plus, instead of contributing the cash you earn, you can contribute an amount of appreciated taxable portfolio assets of equal value (allowing you to take a deduction for the full market value
and avoid capital gains tax), and replace them with new shares purchased with your income at full market value, thereby permanently stepping up your tax basis.
Double plus, if you establish your own charitable fund (as described in the Jim Collins article I linked to above), you can even allow the contributions to continue to grow on a tax-free basis through investments of your choosing, to be allocated as and when you decide (plus get a host of other benefits outlined in Jim's article). So there goes my idea of maximizing the total contributions by deferring them.
My projected FIRE date is (I believe) similar to yours -- probably within three years or so. I have lots more thinking to do about this. Thanks for planting the seed.