For the purposes of making a new Supes II, SR is totally irrelevant when you think about. Just because it came out, doesn't make it essential. Someone mentioned that it was supposed to be a "vague sequel", and vague is something that it sure is. As a Superman fan, I understand *why* it was made the way it was made, but it's not my fault that WB and Singer decided to do a big-budget-yet-half-assed reboot-slash-sequel instead of going balls-out from the get-go. It's kinda similar to Lucas insisting he "had to" make Menace and Clones boring and loaded with pointless exposition to get to Sith, when he could've done whatever the hell he wanted.

It's more of a jumbled part-sequel, part-remake. There is both overlap and disconnect, so "tying it in" is largely a waste of time. Keeping the stupid super-kiss, even though its removal may improve the old story, just to weakly tie it into a movie that itself weakly ties into the old ones is a waste of time. Excising the kiss doesn't damage the continuity or the story-- Lois doesn't *need* to forget anything. It's the end of the movie-- it could be open-ended as to if she really remembers. As long as it ends with Supes flying off into the distance, the flick's gold. You can acknowledge SR's existence all you want for yourself, but for Superman II.0 purposes, it doesn't need to be a factor. If SR is indeed a "sequel" (which it's not), it should've been stated that Supes was gone TWENTY-five years, since the 21st century world depicted in the movie (not to mention the exact-opposite-of-sassy new Lois attitude) is very far removed from Donner/Lester, as is Returns as a whole. Either way, all of the films revolve around a dude from Krypton in blue tights, so they "tie in" enough...

Should any of the mother footage be left in? It was nice to see all the Brando footage, but I also felt the mother lent a nice touch in places as well in the Lester version.
No for a few reasons.
1) It's inconsistent with S:TM in which Superman talks to Jor-El.
2) Lara did not record her intellect and personality onto the crystals, only Jor-El did.
3) There would be no conclusion to the mother & son relationship as there is with father & son.

While Brando is essential, there is an obvious, strong bond with the mother in part I as well, and her presence could be a nice addition (not replacement). I don't recall anywhere stating that the mother *didn't* record anything for Jor-El, so it's plausable that both his mom and dad imparted wisdom. And there doesn't need to be a "conclusion" with the mother/son relationship-- her love is more simple and unconditional-- there is nothing that needs concluding. The father/son bond, like with many fathers and sons, seems more complex and would still see resolution even with the inclusion of some mom footage.