Personally, I'm not a big fan of gold-backed currencies, for a quick "pros and cons", see the associated wikipedia page: https://en.wikipedia.org/wiki/Gold_standard#Theory
As for the noted advantages of backing a currency with gold, there are ways to gain the same advantages without some of the disadvantages, especially given that we're talking about a cryptocurrency:
- Long-term stability: Most modern blockchain-based cryptocurrencies have a built-in function that determines how fast new currency is produced, for Proof of Work (PoW) based cryptocurrencies, difficulty (https://en.bitcoin.it/wiki/Difficulty) is the most common way to manage inflation/deflation.
- Fixed exchange rates: This is a result of backing the currency with a commodity, not especially by backing it with gold, find a commodity that has the desired stability, without the disadvantages of gold, and you'll have a better candidate for commodity backing than gold.
- Disallowing financial repression: Again, accepting that we're acting within the confines of a cryptocurrency, this is easily achieved, as you can, mathematically and programmatically, link "interst rates" (which can be embedded in the core logic of the currency, especially in Proof of Stake (PoS) currencies) and inflation (by means of controlling the rate of issuance).
There are some of the listed disadvantages of gold-backing that CAN also apply to cryptocurrencies, as they are usually implemented, but if we base the new currency on a well-functioning chain and allow ourselves the freedom to change that source, there are programmatical solutions to most of these, I have included a single, cherry-picked example below:
Limit on economic growth: Given that we limit the inflation by providing a stable rate of issuance, we also have put a fixed upper limit on the growth of the economic growth (i.e. we can set the rate of issuance (and by extension, the inflation) at, as a completely fabricated example, 10% per year, but then it turns out that our economic growth has a potential of more than 10% per year, and then we're, more or less, in the same predicament as if we'd been using a gold-backed currency). This can, however, be remedied by sacrificing some transparency. The maximum "rate of issuance" of gold is the rate at which the physical gold can be mined, but we can control the rate of issuance of the cryptocurrency programmatically, letting it be dynamic rather than static, that way, if needed, we can exert some control over rate of issuance, at the price of lowered trust in the currency, as it is now controlled by people instead of computer. This could, again, to some extent, be countered by making these adjustments difficult, for instance, requiring a public vote or 80% unanimity in parliament.