^AntG .. it's not even part of the course but sadly for the reasons you mention there have been 2 fatal accidents in the area of the unrestricted Sloc Road, not sure why spending a load of money to travel and speed around The Sloc seems a good idea.
I'm Manx and have been spectating/spannering/racing for 40 odd years now and this year the weather was the most constant nadgery 'orrible cold/windy/wet/grey weather over the TT fortnight or MGP I can rememberhopefully it's a one-off, it wasn't comfortable/enjoyable to be out there on a bike most of the time nor sat in a field waiting for practice/racing which may explain a lack of bikes, I also noticed that while still being keen and getting to fave spec areas very early there wasn't the usual numbers in attendance until closer to roads closing and a couple of times when out on my bike in relatively clearer weather the TT course was compared to other years totally dead even over the mountain section, the lack of radios/radio noise may have been due to more people using headphones from mobile phones.

The racing classes are much alike but not sure what the answer is -
Moto2/3 bikes are expensive and not raced in great numbers in the UK.
I can see some riders in near future being quicker on Superstock than Superbike due to power/spec etc of latest 1000cc bikes, at at a local sponsors night before TT Hicky was there and he said this years over the counter retail BMW 1000rr has the same bhp as his fully spec'd 2016 BSB bike.
Triumph supply the 765cc Moto2 control engine but have no plans for a sports road bike until 2020 at earliest have already dropped their 675 Daytona sports bike and if they make a 765cc road bike will that be allowed in with 600cc 4-cyl Supersport ?
The current classes are supported by riders who can race regularly at club/national level and road circuits on their bikes, not sure where we'd get a relatively full grid of any other machine or cc from ?.
Sales of 600cc sportsbikes are not good and I think only Yamaha has a new model 600/R6 in the showroom while the Kawasaki is a refreshed bike.
Back "in the day" we started and raced in very wet conditions as it was the done thing then, MGP 90/92 some races we set off in very windy/wet conditions, not saying it was a good idea but it was our choice, these days it's not safe with the speed/power of the bikes and there's much more focus on insurance and health n safety for racers/crew, spectators and land owners.
I'm fortunate to have family on IoM, still enjoy all aspects of TT/MGP and I have huge respect for anybody that comes over and stays/camps in a tent given the conditions this year and would have to say that all the people I met who were camping were very happy just to be here spectating and it's good to still see large numbers of continental fans here.
Sod's Law imposed and the wind has dropped and sun is out today, luckily i'm here for another week.