Hmm, I must have missed these questions.
I'll try and answer to the best of my knowledge.
a] Why is Peter still slimed in the elevator, post-Slimer in the trailers and promo footage, but yet not in the actual game? It would make sense that he is still slimed, but I'm sure it was do to the face being able to be “read” properly.
The slime is a dynamic element that was done in-game. What I speculate happened was this:
All the cinemats were rendered in-game, sans the very high quality ones. Each of the in-game cinemats were contained in their own level. The scene you mentioned probably started after he got slimed. If that was the case, then the special level created to render the scene probably didn't have the scene of Peter getting slimed, thus the missing slime.
As the game development progressed, certain scenes were made pre-rendered because of memory budgets. Originally, this scene was real time but had to be made a pre-rendered cinemat in the end.
b] What was the decision process like about introducing the new equipment upgrades? They just kinda appear, where they weren't there before, unlike the Wii/PS2 versions, which introduce them in the lab proper…
I didn't really have anything to do with this, but I remember we had scenes where Egon would equip you with the new weapons. I think it was just the flow of the story and pacing that made it be the way it was.
c] Judging by the accounts of the panel, and what was said, this version of the game was to include alot if not all of the stuff that was included in the Wii/PS2 versions , such as the Slime Lab technicians, and a number of the other ghosts that were in that iteration, but not this one…What was the reason so many of the ghosts were cut, and would we have seen the ghost dino, the terror dog minis, the 8-Bit arcade ghosts, and the snot hags?
Well, it's a tale of two games being developed in two different cities with two different creative teams. The Wii team had our general story and were able to add in their own twists. They could also get away with sillier ghosts than we could.
The reason so many ghosts got cut was just time. Sometimes you just have to go in and cut your losses. Memory limitations also limit the amount of things you can load per level, so you have to pick and choose what will fit the scene best.
The 4 ghosts you mentioned were never in our development plans.
d] In the game Peter, in the museum cutscene , he slimes him using the Slimeblower MKII, yet in the promo footage he fires his neutrona wand at him…Reason for the change? Or was Peter originally suppossed to be firing at something else?
I have no idea. Probably just a mess up with the particles. The original high quality cinematics had a lot of errors because of time.
e] There was more exposition via cut scenes in the Wii/PS2 versions…Was this part of the concious decision to keep the gamer “in” the game and feeling like one of the guys, or was it just budgetary?
I can only imagine it was the memory limits of the Wii and PS2, mainly the latter. They can only buffer so much dialog.