Continuing my discussion...

#1. security; the problem I suggest isn't security with the bitcoin network.  It's YOUR security.  Real world bad guys can see YOUR bitcoin balance worthy of their efforts; starts cutting off your fingers and flesh until you transfer your funds.  You didn't need those arms nor legs anyway.  We'll call you Stumpy.  CURRENTLY in the real world; why aren't you walking around the streets with wads of money hanging out your pockets?  This is exactly what you are doing with bitcoin.  Once you are personally connected to a wallet (all it takes is one stupid mistake), there is no safe/secure way to completely hide again.  I think you an idiot if you believe you can receive/send payments without anybody knowing who you are.  Anonymous payments in and out?  Really?  Real world doesn't work that way.  Even criminals can't pull that off.  YOU are not good enough to never make a mistake.

#2. fungible. I deem you an idiot if you think bitcoin is really fungible.  The CURRENT network mostly treats bitcoin as  fungible.  But this is changing, and, "tainted" coins and wallets in the future will be treated differently, especially at OFF-RAMPS.  Example; you being a naive idiot thinking your bitcoins are fully fungible; you then pay them to somebody and they are CONFISCATED.  Ha ha, jokes on you.  I'm sure there will be plenty of good excuses for confiscating your coins.  You never really know if your coins will be confiscated until AFTER you send them.

I'm hoping somebody makes a bitcoin PRIVACY hard fork; sooner than later.  Afterward, the market will figure out the rest.

Security (okay "privacy"), also goes the other way...  In the future; (I expect near future), all official/commercial payments will be digital.  This means of course YOU can be financially cancelled as a person, at any time by governments and businesses.  YOU can be black-listed in the real world.  Persona non grata. Your bank accounts froze, debit cards, credit cards frozen, your bitcoin account black-listed.  Perhaps your great grandad owned a "slave", and your whole family gets black-listed.  Perhaps you own real estate that was once stolen "conquered" from another nation.  Maybe you are caught eating dead animals (meat).  Maybe you were peaceful protesting somewhere.  Maybe somebody calls you a racist.  Who knows what "normal" today is that will make you a villain/target in the future.  Regardless of reason you will be a target for future black-listing; privacy is really important, and a natural feature that all good cryptocurrancies should automatically solve.  No smart person shows the world their wallet full of cash, nor bank/financial transactions.  Why would anybody purposely seek out a cryptocurrency (bitcoin) that does exactly that?  Bitcoin can't be everything to everybody.  But to grow up and be a real world cryptocurrency, privacy seems to me should be the high priority.  I can't solve this issue, but if somebody with the ability created a hard-fork; I'm certain the "market" will choose how to sort it all out.

#1. security.  When you make a bitcoin payment; that one payment address then forever connects you to your wallet thus allows the receiving person to see all your previous receives/sends, and, all your future receives/sends.  Any payment you received, or spent, then crushes your anonymity.  You are forever outed; fully exposed.  Really, it's no different than everyone in the world watching your bank account; seeing all the payments coming in and going out.  Bottom line is you can never send or receive a payment to anyone in the real world.  Your bitcoins/activity will forever be linked to you.  Chainalysis perfectly lays out the problem.

#2. non-fungable.  We like to think of bitcoins as being fully fungable.  But the reality is that any bitcoin wallet/coin can be black-listed or otherwise "tainted".  Your wallet could be black listed for any reason, or by mistake with no recourse.  Black-listing means that anybody can create a list containing your wallet address, and then any bitcoins in that address, OR, any bitcoin that ever TOUCHED that address can forever more be treated differently.  If YOU are found to have ever "touched" a black-listed coin, or coin from a black-listed wallet, you could then be targeted, hunted down, your real world accounts/property froze/taken; you arrested, who knows what.  Regardless, not all bitcoins are perceived to be "equal".  And, EVERY bitcoin has a history trail (moving from wallet to wallet) that anybody can easily follow see #1 above.

Bitcoin can never really be great unless every coin is truly fungable.  AND, to be fungable then coins must not be trackable.  Yes, some "alt coins" try to deal with the above.  But ALL mainstream cyrpto currencies especially BITCOIN need to start taking these issues seriously.

Your 24 word seed phrase, each word will be one of these 2048 words listed in BIP39:
https://github.com/bitcoin/bips/blob/master/bip-0039/english.txt

Look up each of your "REAL" words in the list above, and write down the next "FAKE" word that comes AFTER each real word  (or what ever formula you choose that to easily calculate to the real word).  You will now have a list of 24 fake words.  Carry multiple copies of this fake 24 word list with you.  ALSO, password protect (or not, but less secure) your fake list file and email it to yourself, and post it elsewhere/everywhere on the internet.

When you get to your destination, just download the BIP39 word list, then substitute the fake words for the real words, reversing of course what ever formula you used.

The above is a completely secure, easy to use method, allowing you to either carry, or, not to carry anything physical with you.  You could wash up on the shore naked anywhere that has an internet connection, and re-get full access to your bitcoins.