Let's say an agreement was made among all the major Bitcoin exchanges. Starting January 1, a Bitcoin is worth $5000 USD, plain and simple, and that's it. The price never goes higher or lower. A Bitcoin is $5000 today, tomorrow, next week, next month, etc. NOTHING changes it. Not a war, not the economy, not Trump getting re-elected (which he will, he's doing a great job), nothing.
I wonder if that could be done and what the effect would be.
This is out of basics of economics. Who we are to do that ? Only Apple may fix the price of Iphone X. But, USA government should not try to fix price of gold. You are talking like we are the creator and and to fix a value for bitcoins. Might be if Satoshi would have been thought this way then he might have done that. But Satoshi might have thought about deciding value of bitcoins based on market demands because this is how value of everything in this world is being fixed.