Coin destruction certainly exists, but it isn't a problem. So far, no one but you seems to have taken any offense to it. Why do you think it is a problem?
Because a) it's good to know exactly how many coins will be/are in circulation b) the number of bitcoins has a hard capped limit and if enough are destroyed it will make it difficult to function properly as a currency. Why are you so against fixing the issue?
a) true, but so what? Also, impossible.
b) false, so long as destroyed < 100%
It is a pointless change. Yes, I said change. Not a problem. Not an issue. A change.
Do you understand the value now?
You could do this fairly easily with Shamir's secret sharing algorithm. Just generate 4 shares of a single SHA256 private key with 2 shares required for reconstruction. You keep one, the bank keeps one and two go in the vault.
Or even more straight forward just code this type of transaction into the client. Yes you will need to update, but i expect the scripting will require updates as well. At the moment not even the main bitcoin client has all the script operands enabled, Bitcoinj only supports 7. As different clients become more popular it will be difficult to ensure scripts are fully supported.
Yes, this one example can be done in many ways. But I think you missed the key point of my previous post. I'll repeat it here:
All of this can be done using the scripting system, and without anyone in the entire network having to update their client to allow it specifically
The scripts allow anyone, anywhere to devise their own systems without seeking permission from the rest of the world. I guess if you don't see that as a useful feature, I'm not going to waste any time trying to convince you. But then again, I don't need to either. You are the one asking the world to change.
By the way, these two topics have been discussed to death on these forums. Search for "demurrage" and "script".