This is very interesting information that would have effected a great deal surrounding Willow.
* The inevitable breakdown of Willow's fragile character.
It seems likely that to lose the first boy who had ever been attracted to her would either completely break her down or turn her into something of her alternate reality counterpart. I could see her losing most of her rational sense and burying herself in dark magic with greif and guilt. The Willow we know who usually stands timidly at the sidelines might flared up into more of a fighter. If anyone here has watched
Charmed recall the season 6 episode 'Witchstock', what turned anti-violence Flower Child Grams into demon ass-kicking Grams (before Paige had accidentally changed it)? She might possibly even consider if not attempt the ritual to raise the dead which has already been used by Sunnydale high students before.
* The restoration of Angel's Soul
Willow has always been a selfless, considerate and open minded soul but if Angelus had effected her so personally she would be more against him and less willing to restore his soul. To be honest I am not even sure Buffy would try to convince her. I can see her wanting his death for a while during her dark period which would result in more damage during the prolonged wait but Willow is the kind of unique and sensitive person who can see the big picture, the hidden victim in Angel and especially herself reflected in Buffy's loss of him. She would see the chance Buffy had that she did not, the chance to save her love. After all in the actual events Willow performed the ritual mostly of her own accord while Buffy had every intention of killing Angelus.
* Willow's relationship with Xander
With Oz gone I don't believe Willow would have been so resilient to the forbidden flame that had sparked between her and Xander. With nothing to hold her back anymore she probably would have fallen back onto her previous attraction to her long time best friend and the only other boy to whom she wasn't invisible or just 'the nerd girl'. Something certainly would have grown there, despite his respect for Cordelia I have to doubt she would have held Xander back from an unoccupied Willow.
Totally off subject but I must say I am annoyed that it's when she has a boyfriend that he FINALLY notices her that way! How could he have been so blond to her attraction to him!?
The original plan was also to kill Jenny in Innocence -- that went along with Oz dying in Passion. So, take the two into consideration, and...
Wait, without Jenny, where would they get the method to restore Angel's soul?
If they came up with something to get around that idea, then by the time the show reached the middle of Season 4, it would've evened out and played out, from there, pretty much the same as it does already. If not... things become very different.
I don't think that would have changed but rather have occurred earlier.
Can you please explain what you meant that Oz's death was supposed to "go along with" Jenny's? Do we know the details of Oz's removed death?