Harold Ramis' daughter has voiced her opinion about the possibility of a CGI Egon appearing in a Ghostbusters sequel. For a long time after Ghostbusters 2 there was talk of a direct followup. Speculation about original actors' involvement and possible storylines could be found around the Internet for years. Instead, the franchise was rebooted, with the still-living original Ghostbusters cast members showing their solidarity by way of cameo appearances. Unfortunately, Harold Ramis had passed away before the film was made, though he still made an appearance in the reboot (by way of a bust of his head).
At San Diego Comic-Con 2017, Ghostbusters 1&2 director Ivan Reitman spoke about the possibility of making another Ghostbusters film - though whether it would be a sequel to the reboot or something else, is still up in the air. When he was asked about the idea of Ramis' character Egon appearing in this new movie, Reitman mentioned that the idea of using a CGI version of the late actor, in order to include his popular character, was being considered.
In response to Reitman's suggestion, Violet Ramis Stiel - Ramis' daughter - told THR how she felt about the possibility of her father appearing in a new Ghostbusters film through the use of modern technology:
"It's bizarre. Personally, for me, it is hard to imagine that people would accept it, but who knows. The technology now is amazing."
"I try to think what would he have thought. If it's great and it works, then good. And if there is a problem, then obviously no."
The character of Egon was responsible for many of the biggest laughs in the first two Ghostbusters movies. The brilliant yet socially awkward character spouted dry one-liners throughout the films, frequently stealing scenes from popular comedians Bill Murray and Dan Aykroyd. If there is a Ghostbusters 3 in the works, not having Egon would have a definite effect on the tone and feel of the movie. However, not everyone believes in using CGI to bring actors/characters 'back from the dead', so to speak.
The same technology was used in Rogue One: A Star Wars Story in order to bring back the character of Grand Moff Tarkin (played by the late Peter Cushing). Some were impressed by how well the technology worked, but others felt that it was disrespectful to the actor's memory. Cushing's estate did approve the stunt ahead of time, and it sounds like Ramis Stiel is also offering her approval too - provided that the quality of the effect is good.