I think fun should always come first and game mechnics only second. Why implementing weight mechanics (for gold) if it doesn't the fun you have while playing the game? Weight limitations for money is imo quite senseless since you could always barter large amount of coins for some of higher value (like silver coins -> gold coins) of even for some very valuable things like jewelry (rings, chains etc)which you could sell if you need money for buying something else. Weight limitations for money would increase the world coherency but at the cost of endless running from one merchant to another to buy or sell things (which is quite boring imo).
