There are perhaps three main approaches that one can take with the idea of reduced tail risks through FX diversification:
-The Taleb method. He owns the actual bonds and currencies with the bulk of his portfolio. Those positions are cash-like, he is just trying to keep up with inflation and not produce significant returns
-The Dalio method. Dalio doesn't want cash because cash will lose to assets most of the time over the long-run. But he is also all for reducing the risk of ruin and diversifying away risks. So in a portfolio, he would allocate a certain percentage (say 30-40%) of the underlying categories (stocks, bonds, etc) to foreign assets of those categories. So his 30% stock allocation could be 15% US 10% Developed 5% Emerging. Or something along those lines
-And the third method, which is the method that I have been using quite a bit. Which is to own most of my assets in USD and 'redonominate' them into the currencies that I want to own because I believe they are appropriate given the state of the world and my risk preferences. Back a few years ago when I wasn't aware that I could just buy BRL futures and roll over them (for some reason everytime I would pull up the liquidity was shit and I would think they sucked) I decided to use the AUD, NZD, CAD and NOK (commodity currencies) as proxies for the BRL, I did it on Oanda. So most of my assets where in short-term UST bonds but they were 'redenomitated' in those currencies. I would get the interest from the US bonds, plus the positive carry from those currencies (which back during the commodity boom were paying pretty good interest). When 2008 hit and commodities started to plunge, I changed the weightings a bit to focus more on defensive countries. So I added the CHF to the basket (and IIRC, the JPY as well), etc. It was a way to 'outperform' the BRL and produce am extra return. When things stabilized in 2009/2010 I was back in the commodity currencies full on and even implemented a 'beta' component to reflect that the BRL moves more and pays more interest than the AUD, NZD, CAD, NOK. So I used some leverage to 'beta weight' my basket.
Not that this sorts of interventions are recommended, I did it because I just can't help it sometimes. But the overall idea is to own assets in a Dalio like fashion (a balanced approach) but redonominate them into the appropriate currencies that are likely to reward owners and avoid currencies that are about to be devalued.
This third method is a bit more complex but I think its a good idea as an additional tool in the toolbox for a trader/investor/money manager