I work at SnF as a volunteer in Air Operations, so I am familiar with a few of the topics brought up in this thread. While I don't speak officially for the SnF staff, I bet I can answer a few of your questions.
Burning the grass...this was done to prevent a grass fire potential. But it was absolutely hated by our visiting pilots and John "Lites" Leenhouts, the SnF President,stated four years ago that we will no longer do this. And we haven't! (I will "throw myself on the sword" to ensure this never changes, by the way...that soot gets into everything.)
That big fence at HB parking was placed there as a result of ongoing security concerns by the airport with events OTHER than SnF. The SnF grounds are used by many other events throughout the year, so it was one way for the airport management to control those who should not access the rest of the airport.
Sitting by that fence during arrivals: This was an enjoyable pass-time for many, and I too enjoyed sitting out by the previous (e.g. low) fence and watching the constant stream of aircraft landing. However, SnF is a big event and sometimes one area is affected greatly by another's issues, and this is no exception. Specifically, the FAA has experienced changes in their 8900.1 document that governs aerial events, and these changes brought up new non-compliance issues with the SnF "Showcase" fly by pattern. That pattern, normally flown at 500 AGL and parallel/south of normal landing traffic, overflys HB parking on it's way past the crowd, and is used by manufacturers to show off their new wares.
Because of the proximity of this pattern to the HB parking, the FAA was concerned that we now had a de facto "spectator area" in that area. The FAA agreed that we could continue to use that showcase pattern altitude and ground track ONLY if we did not allow bystanders to linger in the HB parking area. That means that we can no longer allow people to sit out at the edge of the fence line and watch landing traffic during the showcase fly by pattern times of 1100-1300. The HB parking area is deemed a "transit" area for our visiting pilots, which still allows us to use it as a parking area but now keeps us legal for the Showcase pattern. It's a solution that impacts many, but we had to make a change that was best for the whole of our SnF visitors.
Taxi times: construction of the new taxiway Delta (which parallels 9R/27L) should speed taxi times remarkably. Should....this is our first year with it, so we hope this works better for all.
Most of all we want to provide the best of all worlds for our visitors. Let me know what we can do to help!