I think it is still prudent to investigate is it is possible using scripting. If so, it would be a double-spend attack with a potentially years-long lag time.
Phillip could you rephrase or Elaborate? I don't understand.
I looked at the scripting opcodes and my eyes kind of glazed over. I am currently assuming
an automated loan is not possible.
The reason I am potentially concerned about a double-spend attack is what happens if somebody uses these bonds to buy goods or services? On the appointed date, they would "cash out," leaving the bond-holder with nothing.
Thinking about it a little more, I decided a customized client is probably needed to use "weird" scripts anyway. The default Bitcoin client probably mainly sticks to "standard" transactions, which are also scripts. Again, I have not carefully checked if my impressions are true or not. The default client will relay "weird" transactions with no problem as far as I can tell.
One issue is that forking is an unknown. No one can be sure hoow smoothly it will occur. I would like to see a demonstration of this because I view forking as one of the best features of the technology. It promises to provide some protection from obsolescence of the underlyong bitcoin technology. Can it fulfill this promise? I want to see a demonstration.
A "Fork" in the traditional sense won't work: it is all or nothing. The clients not recognizing the fork will studiously ignore it.
That said, there is reason to believe that if there is a compelling reason, all (or at least the majority) of the participants can agree to a protocol change. If the change is not urgent, it can take place with decades of lead time. However, in order to get the (vast) majority to agree, the change should be non-controversial. I think your bond proposal would be too controversial to gain widespread acceptance for a protocol change. A non-controversial change would be something like: changing the hash function if collisions are demonstrated with SHA-256. Or, possibly, increasing the sub-divisibility beyond 8 decimal places if too many bitcoins are lost over the years.
Edit: I already explained why I think these non-controversial changes won't happen: I think bitcoin fail (and be replaced with something better) before the specific design choices become too inconvenient. (That is to say, I don't think Bitcoin will fail based on its own technical merits.)