In an ideal world, the footage of Rebels and other cartoons could be used, but the change in style is simply too jarring to pull that off. Same with most Video games, which is sad that it is too different to use.
I’d say EA’s Battlefront is close enough, so long as you don’t see any faces. Then again, the same could be said about CG Tarkin. If Tarkin is passable, maybe we just ignore the same slight offness in the Battlefront faces and use footage from that. It would provide at least 2 hours worth of content to fill the otherwise jarring gap between RotJ and TFA.
Clone wars arcs???
The visuals need to remain roughly the same throughout. We can’t use the stylized CW (either version), Rebels, or Forces of Destiny (bet you forgot that was a thing), but we can use the photorealistic CG cinematics of EA Battlefront 2, and, as you brilliantly suggest, the OR trailers. I would try to avoid time skips though. Part of what makes this project interesting is that it would theoretically flow seemlessly from TPM or earlier up to Episode IX, without any significant time skips. Not exactly sure what parts of the OR trailers would be really usable, though.