The front seat of a Chieftain at night, in IMC, with CBs out there "somewhere" is a very lonely place to be, even if there's 9 other bods on board
Isn't that the truth.
I am currently in a job where this thread vry much applies, however I am lucky that all of our aircraft have WX radars. Whether they work on any given day is another issue, howver most of the time they are a BIG help.
Personally (although I haven't been around for thousands of hours so take of this what you will), I will never go into IMC if I know that embedded CB's are around unless I have a WX radar AND the thing is working. If the CB's aren't embedded and its during the day- then you would be stupid not to go and just pick your way around them. If its at night- then see WX radar comment!
As for turbulence, I am lucky I havent been backed into a corner in regards to having a route which gives no option for avoiding the SIGMET severe turbulence areas. Its probably a different story in Victoria or eastern NSW where is the prevailing winds are coming from a certain direction then your SIGMET would cover a pretty large area.
I have found that quite often a sh#thouse weather forecast on the face of it can actually be deciphered into giving you a route/altitude/time which will result in not quite so sh#thouse conditions.