I know that very high impedances are very bad for noise but i dont konow what is Russell's enviroment.
My circuit is not adjusted, is only an idea. I used that logic with other values in a less radical design for 10-90 V dc and works fine.
I never want to say that my idea is better than other.
The cuestion is that the term 'obvious' is not very obvious, depends if he need keep out the noise, if he want a simple solution etc.
And i think that fets are unique for a lot of aplications, so i'm going to become a fan of them in short time.

Regards.