I agree that Peter wanting revenge on the Sandman is a good part of the story, but it's just not enough to justify that entire other subplot... Sandman's origin, his crime spree and daughter subplot are ridiculous and do not fit in the film at all - it just adds length and takes you away from the main story. Even with more Sandman footage on a DVD release, it's still going to drag the movie down as being too long and too scattered. As much as the 5 minutes of the revenge story does work, it's not enough to justify his entire subplot and, of course, the idiodic notion that someone ELSE killed Peter's uncle.

Even without the revenge sublot, you still have a very good, focused movie about a strained relationship and the temptation of "the dark side."

Cutting out Venom would leave you with no resolution to the black suit story.

I suppose there are three basic approaches to fan editing S3:

1. put back in all the deleted scenes (can someone say A Digitial Man?) which won't really help the film much but may make the Sandman story work a little better
2. Cut out Sandman entirely and see if the film can work focused on the black suit and venom (may be really tricky because sandman is a big part of the final battle... although the scene with Spidey facing off Venom in that building is pretty much self-contained, so it may work)
3. If there is enough extra Sandman material on the DVD, try to make that story work and cut out Venom (may have same problems - or worse - cutting him out of that final battle)

Personally, I think cutting Sandman is the only way to go, because it's the only way to cut a decent amount of running time from the film (which it needs) and if you cut Venom, you basically have to cut the entire climax of the film (the final confrontation is caging and killing Venom).

In any cut, I think a bunch of trimming needs to be done on the Harry/Goblin Jr story. Much of it works and of course the love triangle element is important, but some of the fight stuff (especially the first one) is just ridiculous.

And, please, I think it must be said that it is the responsibility of ALL FAN EDITS OF SPIDERMAN 3 to cut the scene where the butler tells Harry that Peter didn't kill his dad. That was so AWFUL! It stank of a last minute addition to make things way too blindingly obvious.