About the defaltion spiral topic, the human nature of thinking is: If this thing is going up in value, I'm going to hold to it and wait until it gets more valuable
So, in order to counter this kind of thinking, there could be a devaluate design, say if you hold a BTC for more than 3 month, it will disappear
I understand your point, but forcing people to spend their money won't improve the economy. It will drive people away from using it.
The focus should be on creating a compelling application, that people want to spend their money on.
The price of BTC is somewhat irrelevant. If a product is good enough, people will spend.