You sir deserve a cookie.
That's exactly what I've been requesting for years!
In reality, whack on a truck turbo on a little Charade, car won't move. Whack in a massive cam into an engine with an ultra low compression ratio, car won't even idle. 1000hp motor without a beefed up diff or gearbox equals blown parts strewn across the track.
You would have consequences for a bad upgrade or tuning decision. Blown motors,blown turbos,oil and water blowouts, temp problems, ignition problems...etc.
I would also love to have the ability to really concentrate on building a bulletproof motor and driveline in indiviual steps:
Bore,hone,deck,grout filling,4 bolt main conversions,dome,flat or dish top pistons,stud or shaft roller rockers,milling and porting heads,valve sizes,thinner gaskets,high or low rise manifolds,port matching,injecting a carby motor and vice versa,6/71 or 8/71 blowers with pulley sizes etc..
Gearbox and diff mods such as corvette servos,manualized auto's, big or small stall converters, transbrakes,Powerglides, Muncies, Borg Warners, 9 inch diff conversions,mini tubs,link rears,strengthened tailshafts, wide rubber, cheesecutters at the front..etc..etc..etc
I know that's all too much for a console game aimed at the masses but boy oh boy, wouldn't it be wonderful if the world was Wonderland!