First, again, the release date was not arbitrary, but the fact that Paramount had pre-booked it with theater chains meant they were legally bound to release it by Dec. 7, 1979, and subject to lawsuit if they didn't. That the film ran into so many problems means the Producers fumbled badly and didn't deal with the production problems in an effective manner. They could easily have whacked 40% of the effects shots and saved time and money and probably ended up with a better film.
As to Wise's re-edit. I think it's safe to say that the DE is no such thing. We've discussed it again and again, and the DE feels like a fan edit that Wise said yes to. There's some good editorial choices and a lot of head scratchers.