Tobi fights all of the 10 Espada One by one.
He fights Yammy pre-release first, and then makes his way down the list to Yammy again, but released to the 0 Espada.
If speed is an issue(which I don't think it is), then equalize speed for whatever fight the community thinks is unfair(to make this more a fight of skill and ability than speed).
All Rinnegan and Sharingan abilities are available to Tobi. Even Izanagi and creating different paths like both he and Nagato did.
So, can Tobi win against all Espada?
FINAL CHALLENGE - If he can make it through, Tobi vs. All 10 Espada at once(speed equalized if needed).