It was in jest. I don't think you'll ever manage to get that Audi solidness feel, but if you're talking about handling, then there's a lot you can do with the suspension.
Strut brace, stiffer shocks (Koni adjustables), lower stiffer springs (Eibach - which are 'progressive' so not too uncomfortable during normal driving) and an uprated anti-roll bar kit, again, Eibach usually cater for all models. If it fits, you could opt for the GTA antiroll bar kit, but the 147 GTA might be a wider track.
All of the above along with bigger wheels and wider tyres (215/225) would make a huge difference in handling. But if it's rigidity you want.....
Roll cage !