That's the point of a basket or an index - to filter out the single security's local issues.
Exactly. So the approach you could use is based on risk tolerance / aversion. I don't see a basket as found in stock-picking, more a set of scales with risk as the risk-neutral as the fulcrum - USD, AUD, NZD at one end, JPY, CHF at the other: EUR is right now only a maybe, near the middle, GBP is out. Anything smaller than JPY or CHF is high-risk.