I believe the "grease tray" is basically an internal heat deflector. Should serve the same purpose, a double wall between the heat and the outside of the smoker. Plus it'll give a gleaner look.
I'm also under the impression that the grommet is being included in all the WSM models.
As for the usefulness of the 14.5" model? HELL YEAH! I plan on getting one unless the price is ridiculous. I'm hoping for a $199 msrp and a real world street price of $149. The 18.5" can be had pretty regularly at $249, and $349 for the 22.5", so here's hoping.