Clowns shoes is a personal opinion.
Personally I think 15's fit the arches just right.

Wide body would be cool but dont over look good looking flares either.

Regardless of the replies this will receive from the uneducated who like to tell you what you are allowed without themselves even knowing, I will tell you.
Body Mods;
The wide body mod of which you describe is allowed in modified production rego (simple) Body mods of this kind only become questionable for registration when it can not easily be determined visually what make and model the vehicle is.
Wheel Track;
In stock form you can only increase wheel track by the above stated amount.
Change stub axles and diff and then wheel track limit is taken off the donor vehicle wheel track minus how far the components are brought in when fitted to the new vehicle. So you can legally have any wheel track you like registered in mod production aslong as you follow the guidelines given by the DOT.
If you think this is incorrect, I recommend you read the guidelines clearly. If you still have trouble reading it, I can cut and paste it to show you.
Transverse Leaf Front;
Rob Souter,
Greg Sutherland,
Jeff Taylor,
John Taylor and the list can go on.
All these people have raced 1000's with this fronted design and seem to have done well.
I believe Qik1000 also still uses this design.
I also believe there is infact little that you need to do to this design to make it work good.
The above names speaks for itself to me.
No ICV class rego required.
The 1000 below runs a CA18 and QLD seems to be able to mod plate any size motor.

At the end of the day, its only a car, and its yours. Start cutting it up. Dont be a sheep.