If my Saruman "slightly" fails a corruption check, and goes fallen, if he (Wormtongue) is at Isengard a homesite (or maybe wherever) he should be able to shift status from Agent to Character.
If not then I should be able to "play" him as a character using Thrall of the Voice, from the board?
Please help me, because I see agents being able to be used more and help future fallen wizards

To me it's just silly when you see your Agent on the board when your Wizard has fallen, and it's sometimes more advantageous to leave him as an agent because you don't have to use you G.I. like 5 in this case, when you only have 15, and he (worm) gets to go from site to site working. When you could "pay" the 5 mind penalty and fully influence him and start giving items or what not to him, say give him a palantir and teach him how to use it, etc.
Just seems like a simple rule change. The reason I ask is it seems like there are not to many rules areas about, when a wizard goes fallen etc.
Like one other question, which I think has not been asked or answered is:
If you include in your SB your optional Fallen-Wizard avatar(s) up to 2, does your deck and sideboard have to abide by the (White Hand rules) 2 of non-uniques, etc, at that point? Because you are not saying you are Fallen Wizard, but you are leaving the door open.
To me I would say if you put your Fallen-Wizards Avatars in SB and start crossing over with Fallen-Wizard (and minion) resources, you have not declared FW status, but your deck and sb need to follow FW rules.
Thanks