OZBUSDRIVER,
Nothing really there to stop you...........some would call you foolish..........others might tell you that they have done it before.
There are some logical reasons as to why it would work. But the design of an instrument approach takes a lot more into account than simply tracking to a point and working out how low you can go. What happens if you suffer an engine failure? What is your 'out' option? etc.....it might work 99% of the time.....but that 1% that it doesn't might kill you and your passengers.
What is your insurance company going to do if you have an accident? Instrument procedures are provided by the state (Aust Govt) who accept liability for them. It is for this reason that it is mandated we must use them and only them.
Also the enroute controller is going to have no idea what you are doing, but he will know you are descending below MSA and will ask if you are visual....what is going to be your response??
Just some things to think about........
Alpha