you have to tax any income in europe,there is no double tax agreement with h.k.( you have to pay the difference between the tax of your residence country and the hong kong tax on top of the hong kong tax if the tax rate at your residence is higher, which is highly likely)
it is not possible for based crew to get a residence visa in h.k.
it really comes down to your choice of residence and the associated tax rate, many guys moved away from high tax countries for that reason, austria e.g. is not bad.the pay scale is not really designed for any further tax after hong kong took it's share
