The viability of this depends on whether she can sell the idea of Yahoo Reborn. To do that, she's going to have to cull a huge number of bad actors from the existing management, PM, engineering, and design staff -- across the board.

The last big move like this I'm aware of was Steve Jobs' Apple take-over, where he managed to turn Apple into a bigger NeXT, and either shunt all the classic Mac OS people to the sidelines, or force them (as much as possible) to adapt.

It wasn't a perfect transition (see: Carbon vs Cocoa and attempts to retire Carbon internally), but it was a pragmatic one, and it worked.

I'm not holding my breath, but it would be a major coup if she can do the same. Unfortunately for her, and unlike Apple's acquisition of NeXT, Yahoo didn't acquire her previous employer -- this would have greatly facilitated the wholesale replacement of entire dysfunctional teams from a new, better talent pool.