What would have happened if Yoda had managed to turn Dooku back to the light in DR

Discuss the potential ramifications

I don't think Dooku was ever in the light at all. He was always very self-centered even as a child and viewed friends as disposable allies. He never possesed a Jedi's compassion or sense of greater duty. It was his ambition to become the greatest Jedi, not serve the greater good. He almost lost control of himself and nearly killed his former friend as a Jedi Knight. The Sith was a natural fit for him. Him turning back would take an incredible amount of contrivance.

Dooku would presumably tell Yoda about Sidious's identity and Order 66. Yoda would alert the Jedi and probably gather Mace Windu and some others to go after Sidious. How that plays out may depend on whether Palpatine senses the deception; if he does, he will probably try to execute Order 66 early and surround himself with security; 66 will probably still catch a few Jedi off-guard but won't have the same efficacy, and then whether he can secure himself against Yoda and a strike team would depend in part on whether Yoda's penetration of his security in RotS was just Sidious being lazy or something. Without the pretense of the "assassination attempt", more prep-time, and with Dooku potentially being able to testify evidence, Sidious is suddenly in a very precarious position (and Anakin likely hasn't gotten to the point where he would turn). If Sidious doesn't sense the deception in time, then he's even more screwed.

Dooku turning to the light would probably force Anakin to either leave the order or flip out and kill him

Dooku tells about Sidious and Order 66. Sidious dies fighting ten thousand jedi.