Will Mecanim accept biped animations saved out to .fbx?

Try it. I'm no animation guru, just giving you the information I have found from a bit of googling related to your question.

Hold my beer...lol

Thanks for holding my beer lol I tryed it and it turns out that you can drag out a biped in max and just animate the biped and then use yor custom character and avatar with the bipeds animation. First try was a bit wonky but with a bit of tweeking ,its a valid option a person can use.

Yes the issue was resolved.

-If you have 3dsMAX and you want use bipeds in Mecanim to animate your custom made characters with you avatars.

-Drag out a Biped in Max and then center it at 0,0,0.

-Animate your biped to your hearts content and then drag select your entire biped and export selected out to Unity as a FBX file.

-In Unity, Select the FBX, go to your animation tab and set up your FBX as a huminoid character and hit apply.

-Click on the FBX and drag and drop your animation in to the animator view and set it as defualt animation.

-code to move/play and Tweet as nessecary.

Cool cool, glad you got it figured out :) If my answer helped you come to this resolution, it would be super cool of you to accept it and vote it up ;) +1 for posting detailed info for others with this issue :D