There are cars like your superb Alpina 2002 which is built up from a real car and is a replica of a documented car. Gerald's Amco Mini is another example.
However, the cars like the Custaxie are potentially another story in that they are presented as a replica but they aren't actually a replica of the car they are meant to replicate. They may look like the original car at 20 paces but internally they are "improved". This is where the problem lies. If they are "improved" then genuine cars in an historic grid are aggrieved because they have gone to the trouble of doing it properly and they want to, as Howard says, "play with similar cars, not some hot rod with carbon fibre, sequential 'box or a later engine".
On the other hand, the "punters" just want to see some action and aren't too concerned whether the cars are hot rodded or not. There is a place for these cars but it probably isn't amongst a grid a genuine cars or accurate replicas??