The thing is, I don't want to take a view unless I actually have one. In normal trading this is fine - no view, no position, I just stay in cash until something comes along. Zero risk, zero vol, zero stress.
An FX portfolio cannot do this. You have to have a position at all times, even when you have no view. This means when your conviction is zero, you will suffer substantial risk for zero return.
I guess the only way to avoid that is just estimate your future liabilities as best you can, and accept the tracking error. Stay in your estimated base currency weightings whenever you do not have a clear view.
When you do have a view, you simply have to express it at the same weighting as you would if it were a pure speculation, and then make this a deviation from your default FX weighting. So for example if you were 50% USD 50% EUR, and you then became a dollar bear, you would say ok if I were running a fund how much size would I want to short the USD in? Let's say it's 40%, then you shift to 10% USD and 90% EUR. Your base position and your speculative view position are effectively managed as two separate entities, but overlap to form a total net exposure (like a long/short equity fund).
So if your home currency collapses, you are basically going to lose some international purchasing power unless you have the balls to put on a huge speculative short position. In compensation, you become relatively rich in local terms. You can't have your cake and eat it.
Summary:
default position = weightings equivalent to your guesstimated personal spending/liabilities in each currency.
when you have no strong view, stick to the default weighting
when you have a strong view, overlay a position of the same size/risk you would take if you were running a directional speculative FX fund, and net them off against the default position to get an overall net exposure.
Possibly an additional guideline would be to scale back exposure whenever a base currency gets 25%+ above PPP, and diversify into a G7 basket with some of your assets. Another option would be a moderate holding in gold, which would provide some protection by default, although at a cost of its own risk and drawbacks (no yield, negative carry, volatility).