Ogame presently has 5 resources: Metal, Crystal, Deuterium, Food and Population. The first 3 are the traditional resources we are all accustomed to(with Energy to power their respective Mines) but the latter two were only just added. Yet its Population that is what got me thinking that perhaps yet another form of resource could be added to the game: Currency. No Universe exists without a global liquid currency and how Ogame has lasted this long without one is beyond me. We've basically resorted to Bartering by placing a strict limit via Trade rates of 3:2:1 or 2:1:1 and varying in-between. Yet with Population via Lifeforms, we **could** introduce liquid currency into Ogame such that Trades can be executed without the need of one side being online to conduct them.
What I had in mind was a new building that is similar to the Space Dock(hence takes up no Planet Real-Estate) that allows a player to place Resources up for sale. The more you upgrade this structure, the more resources that can be placed for sale and the farther out it can see in the Galaxy for offers. Trade Agreements could be added between Players/Alliances, allowing the linking of these Trading Hubs regardless of distance between them. When an offer is placed, a price per unit in Ogame Currency(say Credits or **Spacebucks** yeah I know like that'll happen... **wishful thinking**) and should a player accept would send their Cargo Ships on a Friendly Mission to Buy/Sell. If it's a Buy Mission, they arrive empty, transfer the credits and take the purchased goods without the other participant having to be online. Conversely if it's a Sell Mission, that player would arrive with Goods and deposit them on Planet in question for the given price. How much is exchanged is dependent on how many Credits the Buyer/Seller has at the moment of the exchange.
Yet the question then becomes: How are Credits produced and what to do with all those Credits? Answer: Population, based on Tier, will produce them(Tier 3 > Tier 2 > Tier 1) and the latter I'm not entirely sure. One thought was Ship maintenance as in every Ship, Planetary Defense, IPM/ABM or other unit in the game ought to come with a maintenance cost. Fusion Plants have always come with a Deuterium cost and now Population comes with Food. Perhaps that'd be use-case for a liquid currency since without one, players would generate gobs of cash and have nothing to spend it on but Resources other players put up for sale.
Even so, what are your thoughts on this possibility? I know it's kind of pulling from Ikariam but if you think about it, Ogame Trading has largely been based on a system that is old and in need of something to give it life. If Trading were "automated", the need to worry about "Pushing" is removed since GF can simply impose Credit limits like they did on Ikariam, although freedom on this could be interesting to see if a player can corner the Deuterium market 
