Hi all!
I’d just finished the “beta” version of my script to quickly have a way to handle mental ray string options without have to wait too long. 

The main goal here is not to provide the best integrated/nice UI but avoid to manage mental ray string options “by hands”.
For now, it work for me. Should work for you, but if you have probs, don’t hesitate to post errors (prefered with “Show stack trace” and “Line number in errors” options checked
)
Put the script in your (for example):
C:\Users\userName\Documents\maya\scripts
To use it, open the script editor, create a new Python tab and just paste:
import enjoyMentalRayStringOptions
enjoyMentalRayStringOptions.Ui().create()
Hope you like! 
FG Passes don’t seems to work on Maya 2012. Seems to be a bug of MR.
Release Note:
[ul]
[li]0.98 - Add a lot of new 3.11 string options
[/li][li]0.97 - Add “mila glossy samples” string option in misc
[/li][li]0.96 - Add a lot of new string options
[/li][li]0.95 - Add “light relative scale” string option
[/li][li]0.94 - Many improvments
[/li][li]0.93 - Add finalgather passes.
[/li][li]0.92 - Add iRay string options.
[/li][li]0.91 - Add “samples per object” and “finalgather legacy” options.
[/li][li]0.9 - Original release.
[/li][/ul]
PS: Thanks to Sylvain Berger for his script k_progressiveRendering wich make me start this more general string options manager. 
even in the options doc.
)