Japan has alot of cool cars that didn't make it to Aus, ie. Altezza, Caldina, Vitz RS(echo but with turbo), even early evo/skyline/silvia/etc... meanwhile downunder we got the TRD Aurion, Corolla sportivo and to a lesser Echo sportivo...
Best bet is to talk to the dealer and confirm if any mods will void warranty. From experience, dealers these days will tend to void warranty if anything looks tampered with (well at least Ford).
Maybe try and get a Vitz RS (jdm import) halfcut? http://en.wikipedia.org/wiki/Toyota_Vitz Otherwise its all down to how much power youre after or how much is in the budgets... There are some kits on ebay, but then you need add ECU http://www.ebay.com.au/itm/Yaris-Echo-T25-T28-TURBO-KIT-U-PIPING-CAST-MANIFOLD-SB-/270742343731?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f09805033 http://www.ebay.com.au/itm/OEM-Toyota-Vios-Turbo-Kit-Echo-Yaris-Vitz-xB-xD-/200632161321?pt=Motors_Car_Truck_Parts_Accessories&hash=item2eb69bd429 keep in mind that reliability will also fly out the window
The Jap spec Yaris RS had rear disks. Did a rear disk convo on my ae86 and used the drum proportioning valve, rear disks kept locking up even on light braking.. chucked in the disk prop valve and it fixed the rear locking first issue.
ae92 and ae101 share the same front springs
ran superlow's in my ae82gze and didn't have much problems with wheels 15x7 (195/50) scrubbing... more like the exhaust hitting humps n *****!
(king spring superlow)
the corolla turbo 2 are imports, i think they might use similar 4efte turbo parts found in ep* starlets (also imports but more common, try http://www.austarletclub.com/)