Nicholas J. Michalak said:

Replacing some of the Kamino Prime Minister's dialogue in the cloning facilities can be easy enough if you can keep that dialogue in cutaways to the clones. If you don't see him on the screen, you needn't worry about matching his lip movements. It comes down to the voice matching consistently. It might be necessary to replace all his dialogue to achieve this if it is that crucial to your edit.

-NJM

It's not the redubbing itself that's problematic, but finding suitable responses from Obi Wan that make sense in regard to what he's being told. Even if I did cobble together responses from Ewan Mcgregor's body of work, there are limited cutaways to work with. Plus the fact we need to cut back to him speaking the original dialogue at least at some point, which makes creating new responses even more problematic as they have to be incorporated between some of his existing responses too and therefore must make sense and flow from one to the other.

Any new dialogue for Lama Su would have to be reverse engineered based on what Ewan Dialogue we'd have to work with, if that makes any sense. And even then, you're extremely limited by the cutaways and have to take the original dialogue into account when choosing obi lines......which in turn affects the lama su lines. Yeah, it's pretty confusing.