I think it not appearing until Clemens dies, might be taking it over board, but I do think cutting every scene with the creature before and after the funeral until then would indeed be an inarguably vast improvement.
Despite some amazing looking stuff, in the Boggs and Rains attack scene, it is especially superfluous. I feel similarly about the death of Murphy but even more so.
But certainly I would sooner lose all of that than Clemens discovering Ripley on the beach, and the Assembly opening in general.
Do you keep Murphy looking at Spike or not in this case? Or the scene with Babe but remove the Facehugger shot? Or maybe keep both, create a situation where, you are left guessing which animal actually got impregnated until the funeral. The chestburster scene I would be most reluctant to lose. That and yes the Alien being captured subplot, even if it would be best to trim some scenes after that, particularly the one with Ripley and Dillon in the cell before Morse comes along you can lose entirely.
I am truthfully much more precious about all the additional little characters moments in the Special Edition than any of the big stuff aside from the alternate opening.
Spoiler
I also think we are better without Vincent's many scenes of characterisation and identification by David, painful but it's necessary.
