Could we value BTC as a formulae such as: (World Population X Human work potential in a lifetime) / Total BTC in circulation.
Thus we could then say that a BTC would be worth:
(7.162 Billion people X 10 hours a day X 288 days a year X 50 working years)/ 12,000,000 = 8,594,4000 hours of human labour.
As the number of BTC increases or as the world population decreases, the total worth of human labour per BTC would change accordingly.
If it was agreed by a group body what the 'worth' of a BTC is independent of existing fiat currencies (which are frankly worthless), we could then ignore all Fiat completely and create an economy independent of fiat currencies - trading on a mutually agreed value of a BTC.
It might seem then that a Satoshi would be worth about 1 human hour of labour, but once you take into account what it takes to create something it isn't in the realms of unrealistic.
So to sum up: Value BTC as a function of HUMAN LABOUR POTENTIAL.
Bad or good idea?
I believe one of the failing points of bitcoin is that we constantly want to price it against other fiat currencies and present Bitcoin as a fiat currency itself. Although it shares many qualities of a fiat currency, it also shares more qualities of a hard currency like gold yet all we can quantify it is against the total sum of bitcoins in existence and predicted to exist.
Bitcoin needs to ignore all other money and just become a means of transacting value which is its true purpose. We can't look at it in fiat because when the central bank bullshit blows apart and fails catastrophically, nobody is going to give a shit about fiat currency so you won't be able to buy any with a bag full of $$$'s.
So how much should a BTC be worth valued against something intrinsic? How do we value it more precisely? We could say that if it took over all financial markets it would be worth what the current financial market is worth, yet if it did replace existing financial markets you can no longer define it as being worth so much in USD as they won't exist any more.
Instead it makes more sense to value it against something we can all agree on and which is true to bitcoins nature.
If Bitcoin was the only medium of exchange that might make sense... but unfortunately, I don't think we can take the value of all labor on earth and assign that value to Bitcoin. It might be a good theoretical point to estimate Bitcoin's value if it did replace all other mediums of exchange.