A few comments:

1) the notion of pre-heating the fuel a pinch device is being tried right now at Sandia National Lab. It is call MagLif.
2) The neutrons from fusion, D-D or D-T, are such high energy that they will pass through a plasma of sustainable volume. Even ITER cannot contain its neutrons and it is many times larger than a pinch. The same is true for a NIF fuel pellet that is extremely dense but small.
3) Preheating a plasma in a pinch is not a positive attribute. You want cold fuel to start with. If the fuel is hot, it is difficult to compress to even higher temperatures as radiation becomes an important loss mechanism. Even pre-heating at MagLif is only 100 eV at most. Pre-heating is also an energy intensive process. It might cost more than it benefits.