I get why someone might be interested in those kinds of things, you see these tactics often discussed by more sophisticated FIRE folks and bogleheads. Personally, while I do geek out a bit on this stuff because I like to look at data and crunch numbers as much as the next nerd, many of these are micro-optimizations that take up way more time than they're worth (at least in my specific case, purely anecdotal).

That said, you have to decide who your target user base is - if it's the hardcore optimizer FIRE folks, then yes, building in the capability to at least play those kind of what-if scenarios and maybe do optimizations will probably be important for that user base.

There is another group of folks just looking for a path to lower-case FI, maybe with early retirement, and not treating FIRE as the end goal but rather as a means to an end, that want to follow a not-so-complicated path that will give them that FI but not spend all their time obsessing the numbers. This excellent post Life On Fire – What's Next For Me, You and Us[0] by Vicki Robin of _Your_Money_or_Your_Life_ fame sheds some light on this other group:

"AT THE SAME TIME, I SOON REALIZED THAT FIRE IS ACTUALLY NOT MY TRIBE.
We applied the same methodology to money but it seems for different ends. For me, FI has simply been the freedom to pursue a higher purpose – to grow spiritually, to learn, to create and to serve. While I’ve met a lot of people reaching for relevance in their lives, not just independence, it’s not what people obsess about. They obsess about taxes and investments. There are probably tens of thousands more in my frame, but of necessity investing the majoring of their time and attention into the “getting out” part of the journey."

If you target that group, then I suspect they'll be looking for less in the way of these advanced capabilities to optimize their finances and more in the way of what your app already provides.

I could see some middle ground for offering tools to help make decisions for specific questions / scenarios. I started to sketch out an example of what this might look like for "Should I do a Roth Conversion?" and it might look something like this:

- It would ask for estimated federal and state income tax rates (0% for some states), pre- and post-conversion.

- It would calculate estimated RMDs for different percentages of the projected Traditional IRA balance representing varying Roth conversion percentages (0%, 25%, 50%, 100%), that would be useful and there are a bunch of such RMD calculators out there.

- It could estimate the delta on estimated taxes due to estimated RMD and total the additional taxes due to RMDs up to your life expectancy age (assumes tax your fed and state tax rates stay the same, kind of a wildcard)

- It could estimate how much on average and in aggregate you'd pay in taxes if you converted 25%, 50%, 100% and of your traditional IRA to a Roth over N many years starting at age A (N and A user changeable)

- It could estimate your balances remaining at your life expectancy age broken down by account type ($X in taxable accounts, $Y in tax-deferred, $Z in tax-free) if you converted 0%, 25%, 50%, 100%.

I think that would have to be good enough, though I suppose you could add all sorts of bells and whistles in terms of charts and visualizations to make it easier to understand the data. The data provided would be helpful to make decisions based on various personal judgment calls and preferences: the importance of the highest possible tax-free balance in your estate to be passed along tax-free to beneficiaries; the importance of minimizing overall taxes paid over the various scenarios; your interest in either paying more taxes now or more taxes later; your comfort in doing the conversion on your own; your willingness to pay a professional to do the conversion for you if you don't feel comfortable doing it on your own; your willingness to move from a state with high income tax to a state that has no income tax which would maybe change the numbers enough to make it more reasonable to do a conversion given your other preferences. Those personal preferences would be tough to factor into an optimization calculation, though I suppose a questionnaire to capture preferences like the above (eg "on a scale from 1-3, how important is ...) could be used with a rule-based algorithm to guide the user to a scenario that fits their preferences best.

Whew, sorry for the long-winded example.

[0] https://yourmoneyoryourlife.com/life-on-fire/

EDIT: to improve the bullet formatting, first time trying "bullets" in HN comment!