Gold encumbrance would be an entirely negative mechanic without a viable alternative imo. Though I like the idea of an in game bank - the current one charges 10% of your gold to do anything with it. That's an insane amount. Players who've worked hard for a year or more could lose 50k+ for no reason. That'd be nuts.
I think at a certain point you have to assume a character isn't carrying all their gold around with them at all times and that it's just a game-play thing. After all, if our characters dress down in casual clothing we don't assume they have their backpack and armour on their backs? It's just mechanics and RP > mechanics.
That said, alternative currency systems can be fun and interesting. Coin weight isn't inherently bad. But it has to be a part of a system that adds features and progression, instead of being only a player-punishing trait. For example, banking and trading systems, where you could earn money with investments, either in a bank with interest or by moving gold to property and selling it at a higher value at a later time or in another place, would make it something that's constructive and fun.