Three or four season tent for southwest Tassie?

I'm currently in the market for one or more 3-season hiking tents. I have vague aspirations of doing some southwest Tassie hikes next year. What I'm trying to work out is whether a 3 season tent can be suitable for the SW (eg, eastern/western Arthurs). I've never been there - only the Overland. In fact, although I've done a reasonable amount of hiking around the world (probably 50+ nights), I have very little experience of hiking in heavy, persistent rain, low temperatures, or high wind. Call me lucky, perhaps 
So, a few specific questions:
1) How important is the ability to withstand snow loading, for a summer hike, in the SW? (Snow loading seems to be important to many American review sites - how common is snow in Tassie in summer? Do you get enough that the weight would matter?)
2) Is a 3 season tent with a full mesh inner feasible? Terrible idea? If so, why - because it's just not warm enough?
3) What about a tent with a full fabric inner, but rated as "three season"?
4) What are the specific features of a "four season" tent that are particularly important? Strong poles? Strong fabric? More guy points?
5) Is freestanding-ness important? Again, why - difficulty of finding good sites, or strength in wind, or both?
6) Has anyone here used a 2 man tent under 2kg in the southwest, in bad weather, and not regretted it?
(Various bushwalking friends of mine tell me "You don't want lightweight, you want strong!" - I'm interested in more opinions.)
My current two tents are the McKinley Compact Light (1.9kg 3 season, mesh inner, 2 man, tunnel tent, can be bought around $150 now) and the TarpTent Rainshadow 2 (~1.3kg, 3 man, single skin, massive ventilation, but bad in strong wind).
Basically, I'm trying to work out whether to:
a) Get a 3 season tent that would also be suitable for serious weather hikes in Tassie, or:
b) Just get a lighter 3 season tent, and if/when I go to Tassie, borrow/hire something more serious.
I'm vaguely leaning towards something like this: http://www.rei.com/product/827787/rei-q ... -plus-tent

So, a few specific questions:
1) How important is the ability to withstand snow loading, for a summer hike, in the SW? (Snow loading seems to be important to many American review sites - how common is snow in Tassie in summer? Do you get enough that the weight would matter?)
2) Is a 3 season tent with a full mesh inner feasible? Terrible idea? If so, why - because it's just not warm enough?
3) What about a tent with a full fabric inner, but rated as "three season"?
4) What are the specific features of a "four season" tent that are particularly important? Strong poles? Strong fabric? More guy points?
5) Is freestanding-ness important? Again, why - difficulty of finding good sites, or strength in wind, or both?
6) Has anyone here used a 2 man tent under 2kg in the southwest, in bad weather, and not regretted it?

My current two tents are the McKinley Compact Light (1.9kg 3 season, mesh inner, 2 man, tunnel tent, can be bought around $150 now) and the TarpTent Rainshadow 2 (~1.3kg, 3 man, single skin, massive ventilation, but bad in strong wind).
Basically, I'm trying to work out whether to:
a) Get a 3 season tent that would also be suitable for serious weather hikes in Tassie, or:
b) Just get a lighter 3 season tent, and if/when I go to Tassie, borrow/hire something more serious.
I'm vaguely leaning towards something like this: http://www.rei.com/product/827787/rei-q ... -plus-tent