Siieger,
The Swiss 06/29 lineage of the postwar Mauser is not an assumption. It's a fact.
If Mauser had used the pre-1945 approach the entire project would have been too expensive, making it a complete impossibility in the first place. The P08 required machining steps that were superflous, overly complicated and in some aspects completely idiotic
The market was indeed a problem, although there was one, you are correct to say that it was difficult (nearly impossible) to compete against the surplus Luger market in the USA. The fact that Mauser stuck to some Swiss visual design aspects certainly didn't help.
But that was the choice they had to make: Redesign and use the 06/29 pattern and be somewhat competetive, or don't do it at all. There was no inbetween. The grip safety wasn't a choice, it was a requirement, although shortening it wasn't a good idea. The Swiss longer safety is more ergonomic (won't bite as much)
The thick grips were rectified at a later date, although they never got near the feel of the old ones. Indeed a change they should have made when they had the chance.