Hey Simon,
Welcome to Victoria !
If you are getting into kiting, Port Phillip bay is an excellent place to be.
Winter kiting is fine and you should survive just fine - just wear a wetsuit. I wear a 3:2 in winter and it does me just fine. Last year I invested in a beanie too which was great on really cold mornings kiting before work. Standby for all sorts of advice on drysuits and thicker wetsuits - but I reckon a 3:2 is the minimum you can get by with.
I have a full time job and 2 kids so time is at a premium, but I still manage to get out about twice a week in summer and every 2 weeks in winter. With a Uni schedule you should be able to get out about once a week in winter and heaps in summer (3-4 times a week). A thick steamer would be ambitious in my mind - but you can try it and grab a wetsuit if it doesn't work out for you.
Winds in winter are more frontal (ie. not as consistent and more gusty) and can pack more of a punch (colder temperature, more dense air or something - someone wrote about it in this forum somewhere). If you really want to look at the data, go here for the averages -
www.baywx.com.au/fbeacon.JAN.htmlIn terms of kite sizing, I put together some data a while back based on a lot of peoples opinions
kitesurfing-handbook.peterskiteboarding.com/progression/choosing-the-right-kite-sizeAn 11m and an 8m would be ideal for your weight - but you won't go far wrong with 11 and 7. Just make sure you get a kite that is less than 4 years old so that it has sufficient safety features.
I've never tried a wakeboard with a kite - I think it would be a struggle for a beginner - you would probably want something a bit bigger to start off with.
The handbook above has other info for beginners - best of luck !
Stuart