Personally going off your information and amount of points & status you have already accumulated, I think for your FF future your best bet is to fly international with Singapore, but booked via a Virgin codeshare*, credit the trip to Velocity, Which you can do for your trips to Thailand & Asia from now on, Singapore Airlines has some of the best connections going from Aus-Asia. Plus the service is great.
*Beware depending on how you make this booking it can end up being more expensive than booking it through Singapore airlines itself, but some booking agents can end up being cheaper, you will have to take note of booking class & weigh up your options.
a) Velocity Gold is much easier to achieve than KrisFlyer Gold. With the reciprocal alliance they have together Velocity gold will give you the same perks as KrisFlyer gold, I.e lounge access etc. So I think aiming for velocity gold is perhaps the easiest way to begin with.
b) Future domestic fights booked with Virgin and credited to velocity (if possible/economical/convienent) it will obviously also help you achieve Velocity Gold status and stack points in the one area.
c) future international trips to Europe etc can be travelled on with Singapore or Etihad(to rival emirates) and can also be credited to Velocity.
Also not forgetting the awesome ability to switch miles/points between KrisFlyer & Velocity programs.
Also note “Elite Miles” which are for Krisflyer status, they can’t be earned through flying Domestic Virgin unless the flight is booked through Singapore airlines with a connection through to Singapore on a Singapore Airlines flight.
For e.g if you book just a straight ticket from SYD-MEL with Virgin you can credit the miles to Krisflyer but you don’t earn the valuable “elite miles” for status. But if you credit the flights to velocity you earn the status for velocity.
Saying this from experience, I’m Thai Gold & Qantas Gold… & only now only 1 return trip off of KrisFlyer Gold, what I found difficult, and Inconvienent Is trying to maintain two golds in the one year. I wish that Thai/Qantas had an alliance so I could of kept it all under the one banner. I had straight loyalty because my credit card was qantas & the county is Thailand, but after learning much from frequent flyer sites, and experiencing many different airlines and trying out different reward programs. I made the switch, to go for KrisFlyer Gold & fly Singapore Airlines & Virgin domestically from now on. I also changed credit cards from a qantas points earned into a rewards program card which can be credited to velocity points or KrisFlyer miles. I believe to stack more points in the one area equates to more frequent rewards for the frequent flying. Singapore Airlines also happened to have a better and more frequent schedule than Thai so it just made sense for me to make the switch, it is also more manageable. My Qantas and Thai gold will expire sooner than later but the KrisFlyer/Velocity alliance and products work out better for my needs.
Another option is if your confident and believe you will fly Singapore Airlines enough, you could go for gold in their program, as they are part of Star Alliance, which will open up your flying options in the future as well. But going for gold in Velocity will be much easier to begin with especially if your domestic travels outways international.
There is a lot to read up on this site about Virgin’s Velocity & Singapore’s KrisFlyer. It will give you a more comprehensive understanding.
Here is some links