A "moderate currency weakness" is like "a little inflation"... appears to be a short-term benefit, but whatever benefit it's mostly only nominal. And rarely do the powers in control of the forces stop at "a little"... they press and press... until destruction. It's likely we are near the cusp of all that right now...
I would not disagree with you regarding the slippery slope. It's very tempting and I, personally, expect the govts to succumb to the temptation. However, I do believe that in certain cases (e.g. UK Plc) there's just no alternative, as it's a matter of short-term survival.
Same for the US.... Our Gummint would waste any amount of money and capital to "drag out the decline", thus virtually assuring destruction, rather than take any pain NOW and face being held accountable... I once heard a Federal politico exclaim, "consequences postponed is a problem solved in my book..." While I recall seeing him say it, I don't recall his name... REALLY pissed me off!
How is being able to buy $2 of goods better than being able to buy $1? Answer that and you've answered your question.