I'd recommend taking green out of asia and then attacking austrailia Also evacuate the horn and use those troops to attack asia. You have a significant lead and risk making yourself a target
Holding Oceania would definitely be a plus... but it's a very tight map right now with Red dominant in S.America and Pink looking to take Europe... Green is strong in Asia and Aqua holding South Africa.
IF you are holding a mixed set to cash your bonus is 20 (which is the equivilent of Green's Asia) and if you use it all there(?) Aqua's bonus is 12 plus a possible cash-in to demolish your grip in Africa.
So I suppose you have to decide who is the bigger immediate threat? Aqua or Green? They both have 4 spoils and either one might have a strong response to your aggression... but it's most likely that Aqua will hit you in Africa regardless of what you do. So I think you have to consider your position without The Horn or take action to hold onto it.
You're in kind of a pickle... there's a lot of armies that have to fall before you can control Indonesia and both Green and Aqua are going to be big problems. Because green is a bit more distanced from you, my inclination would be to fort Oz a little and deal with tampen Africa first... if you're able to crush Green in Asia I'd expect Aqua to knock you out of Africa while you are busy with him.
Aqua has 19 armies on The Horn's border... and the 10 on Norwegian Claim could just as easily move east to Oz, so be patient and consider all your options carefully and think about what you'd like to accomplish in the next 3 or 4 moves.
Then again... it's freestyle and both Green & Aqua might move before you and the whole scenario might be altered before you even see the map again.