Mainly size and driving position. The charm of the AWD and live adjustments would need to be kept around but even without the ol turbo you'll still have a small, nimble, darty car to toss around. Something would be lost in the conversion but balancing turbo lag isn't the entire car. The Model 3 is long, wide, with a big wheelbase compared to, especially the older, STi's.

I wouldn't call STIs darty. They're nose heavy and need heavy coaxing with the left foot to rotate. The big wheelbase in the Model 3 is a fair point though. Apparently there are TC/DSC defeat devices and mechanical LSDs available for them now, so I'd expect Model 3s to be rallied more and more as they age out.