Asset allocation and keeping cash as an asset in a foreign currency?

There is two good reasons to view foreign cash as an asset:

1. Forex speculation. If you want to do forex speculation, you need to do it properly with lots of leverage and short term goals. Otherwise just having cash is likely to be eaten away by inflation
2. Hedging against hyperinflation in your local currency. While keeping foreign cash certainly is a sensible decision if you happen to own Turkish lira or something similar, the Euro probably will not be considerably more or less affected by inflation than dollar, pounds or swiss francs.

Do you considering this a sensible choice? My concern is that this might be redundant if we take into account that I already own gold.

It depends on what your expectation on gold is. Gold is a very volatile investment that is not producing any cash flow. If you buy gold cheap and it appreciates, fine. But due to its volatility, gold is not a good inflation hedge. You might just be in for a ride down. Buying foreign bonds or stocks will give you the same hedge against local inflation but as a cash producing asset. Cryptocurrencies in this regard are the same as gold but just with even more volatility.
So personally, I would get rid of any fixed allocation on gold or foreign cash and rather diversify my stock portfolio to include more than just Euro and Dollar stocks.