I just can't get behind covering Egons death in some gloomy way. This isn't an X-Men film with some rainy funeral of ProfessorX, it's a continuation of a mostly light hearted 80s sci-fi comedy. Save the "dark" tones for the spooky stuff.Ghostbusters is a comedy, but they took their death seriously. When they crossed the streams they expected to die and you see them realize this as they say their subtle goodbyes. I can't imagine them taking Egon's death lightly.
Unless it's explained in a comedic way, that I can get behind. Say, he actually drilled his head or he walked into another dimension for science. That's more "in character" with the comedic tones.
If they go with something somber it will suck. If they go with something funny it will suck. They need to go with a heroic sacrifice.