I agree that in theory it would be useful to permit shareholders to specify a quantity of currency to be burned. While it can be done, I have been unable to devise a method that is sufficiently simple and elegant, as complexity in the protocol compromises security and reliability.
Let’s examine what the above proposal by @dongshan would look like in some detail. Shareholders could place a vote to permit a certain quantity of currency at a certain address to be burned in exchange for a certain quantity of NuShares. The vote contains these pieces of data: 1) a currency address, 2) a currency quantity, 3) a NuShare quantity and 4) a NuShare address. If the majority of blocks and share days in a 10,000 block period contained the same value for these four elements it would be considered passed, meaning the exchange of currency for NuShares would occur.
One problem with this is that you are allowing shareholders to destroy someone’s currency, which is not necessarily the will of the currency holder. It could be used to destroy currency at a particular address in exchange for zero NuShares. This is undesirable. To avoid this, we could say the vote doesn’t force the exchange but just permits the owner of the currency to choose the exchange by signing the transaction. In that case, the currency address private key is used to sign a transaction much like I have proposed except that the protocol only permits the exchange if the addresses and amounts have been previously approved by shareholders.
This solution requires that the entity signing the exchange have sufficient funds available to purchase the currency to be burned, whereas my proposal permits an unlimited number of people who already possess currency to exchange it. It also requires a much longer latency between when the exchange rate is chosen and when the exchange is effected (maybe three times as long), which means the exchange rate is likely to be further from the present market rate. Imagine the common scenario where the market value of NuShares declines between the time a proposal is submitted by an entity willing to burn currency and the time that proposal is passed by shareholders. The entity will lose value by signing the exchange, and is therefore likely to decline to do so and submit a new proposal at an updated price.
I have described what I understand as the details of dongshan’s proposal to highlight the deficiencies in hopes that someone can devise a modification that removes them. As presently described, I believe the problems introduced by the proposal are greater than the problems solved.