A sports wagon is totally practical. I can understand the aversion (and that's almost strictly an American thing, as sports wagons are outrageously popular in Europe and Japan, and the rest of the Asian markets aren't developed/matured enough to appreciate cars like this), but saying they're impractical is way off base - just look at the numbers.
Imagine if HRoi replaced his M3 sedan with the E63T wagon - he'd have an E63 and a 997 GT3, that's like a one-two for street/track cars, and as you can see above, the E63 gets slightly better mileage, is much bigger and utilitarian (most people don't ever use the 7 passenger feature, but I would very occasionally) and it's even faster than the M3.