You've said "sailing", so that helps.
Going the "downhill"
route would be EU to
Caribbean to
Panama to
Marquesas to Oz. If you want to be closer to land than the big jumps, then EU to
Egypt to Aden to
India to
Malaysia to Australia means much smaller jumps are possible. On the first
route there's dangers from long jumps,
piracy off
Panama (non-government kind
). On the second route, there's dangers from
piracy off the red sea, and going through more countries that have different rules and costs. Both routes would need careful checks on timings to take most advantage. Via
Asia is shorter (at least to Oz landfall at Darwin!).
Oz to EU is a different beast. You could go
Hawaii and across to US, down to Panama to
Cuba to
Bermuda to
Azores to EU. But the first half would be trickier and need careful planning for
wind. The other way is across the wild and uninhabited expanse of the southern Pacific and up the coast to Panama. Both are longer. Without going Cape of Good Hope, you'd have to either go up
Indonesia and across to Sri Lanka to Aden to Med to EU, but you could
head west across the Indian before going north and visit the
Maldives via Cocos Is and then to Africa/Gulf.
Either way there's not many cruisers who traverse the Gulf of Aden in the last 5 years or so - I think there was less than
20 per annum, as against 300+ for
South Africa. Note that the route does seem to be calming down according to reports (like
noonsite).
We're on a powercat and planning the EU Suez
Asia Oz route "in a few years"...