In my view its all about usability and balance, I like the idea of a stylish classic with some modern comforts but I wouldn't want to take it too far from the original as to me half the fun of a classic is the driving experience. The modified Alfa 105s at over 300k are awesome cars but to use most of the upgrades you need to be on a track, in everyday use is one any better than Batmans old TS engined Giulia saloon which I was tempted to buy at around 12k. Even today a sorted 105 with TS power, decent suspension & brakes and a modern bluetooth sound system hidden away can be had for well under 100k. I always wanted a Fanalone Fulvia, now circa 100k, but in real world everyday use is it 5 times better than my 1.3 Montecarlo? Maybe it is but I get all the fun I want from it and nearly everyone who see's it thinks its a HF.
As much as a relatively new modern interests me I just can't justify the cost and hate the idea of just driving a blob like everyone else. Andy old 325i does everything I need it to and its going up in the cool stakes, a decent E24 or and UR Quattro would be the next level and I would much rather invest 20-40k in one of those that will retain value.