Being a fan of KR since more or less twenty years, I personally think that the biggest mistake the creators of the movie can do is the change the original K.I.T.T. (from the original TV series) to a new model.
Why? The movie will be directed to the main target group of the 14-35 years old. Image the movie with (necessarily) new actors and a completely new designed K.I.T.T.. What would be the result? Those targeted people normally interested in the movie (as they know and like it from former times) will, in that case, certainly look for the "link" to the original series they liked. This link, in my opinion, can only be two fold: The old K.I.T.T. and/or the old cast. Consequently, this can only be the original K.I.T.T. (as, of course, the old actors can and will not play the roles again). If there is no link to the series people remember, they could regard the movie as a totally new one, as some new movie with some "speaking car" (which in my opinion happened to new KR series).
There are several examples that leaving an essential part of a stroy untouched leads to success, i.a.
- Star Trek Movie: The plot was based on a totally different actor crew. However, the creators decided not to change the essential part of the movie: the ENTERPRISE. That could be a reason why people liked the movie as they could build up a connection by the former ENTERPISE ship (which was the same as in the traditional series) used which people simply knew. If they were seeing the ship in trailer, they possibly felt a close connection from (old) memories to the new movie.
- A-Team: As discussed als here: People really liked to see the old Van from the old series. Again, totally different cast, but one stable element: The old Van. Many of my colleagues mentioned that it was great to see that, even only in short scenes.
Back to KR, here it is even more crucial to rely on the old K.I.T.T. as it has such an important role an can even be seen as an "actor" besides Micheal Knight etc.

What do you think?
Christian