Yes. I'd suggest running the Wii through the 990, then run the 990's component output into the component switcher. That gives you a component video connection that can cover both the Wii and the 990's menus.
If you use my idea from above, you'll want to use one of the rear video inputs so you can assign a component video input to it.

Since you have seven devices connected but only one that might want to use the 990's video switching, here's an example that could work:

• DVD: Label "Blu-ray", assign coax2 audio
• Video1: Label "Cable", assign coax1 audio
• Video2: Label "Wii", assign analog audio and component-video1 (although you can use any of the three component inputs)
• Video3: Label "XBox360", assign opt1 audio
• Video4: Label "PS3", assign opt2 audio
• Video5: Label "HD-DVD", assign opt3 audio
• 7.1 Direct: no changes needed, can't edit name
• CD: leave name "CD", assign op4 audio

Aside from needing to have the Wii on either DVD or Video1 through Video4 (so you can have a rear ananlog input paired with one of the component inputs), those can be shuffled around at will.
"Opt1" is the digital input. "CD" (as an example) is the input name, which you can change to say something else (like "CD Changer" or "iPod").