Any plans on restoring the Cyberdemon and the Spider Mastermind?
Short answer: that's incredibly out of my league, unfortunately.
Longer answer: it's possible to place the Cyberdemon in the game. Proof of concept:
Additionally, adjusting his states and abilities can be done with DeHacked, then patch that information into the 32X rom without many issues (DeHacked is primarily rigged for the original Doom and there are pointer mismatches that need to be manually adjusted). The real issues come with how he's placed. As you may have already noticed, the above shots indicate his presence at the expense of replacing an existing enemy. Without the source code and, more damning, not being a programmer myself, it's not something I can do otherwise. I can't even fix the Doomguy's flipping portrait frames
A group of fans did manage to include the Spider Mastermind and fix the Spectre's transparency in the Jaguar version though, along with having music during the levels
, which is nothing short of spectacular.
Of course, this depends on what you'd be replacing. An example: the game has data for Demons and Specters, but since Specters do not use the transparency effects at all like in the original, any Specter entity is indistinguishable from a regular Demon (map editors will read both Demons and Specters in a 32X map but ingame there's no difference). In theory, one could find the Specter animation offsets and exchange them for the Cyberdemon (I have been somewhat successful doing this with other enemies). Doom has a series of unused sprites, from scenery to items, which could be replaced with the Cyberdemon's frames. The space used seems quite negligible, and there are more than enough unused sprites to go around. Another example is this: I've managed to swamp an unused stalagmite with a dead marine's corpse, making it closer to the original game:
Assuming one can do this by repointing it to the sprites not usually considered as animations, then sure... But it would still require replacing the Specter or something else (such as reworking an unused item into a critter, if possible, which would also require associating more frames and states to it). The game uses Things (entities) for enemies and items (even the explosive barrel is considered an entity) and it would be necessary to create a new one. Also, unlike most other enemies who have two death animations, the Cyberdemon has a single long death animation. So even if possible it's not an ideal solution. I assume that one can very carefully rewire the code so that it overwrites unused Things and makes a new one, though.
But let's not forget he has his own sounds as well and while Saxman's notes point out to their starting location in the ROM, and I've been cataloguing them for the past week, their format eludes me so I'm not sure how they could be properly transfered. The 32X version has around 50 sounds (54 if you count the menu sounds) and repeats two of them: it has 2 virtually identical versions of the shotgun reload sound (the sound you hear on any weapon pickup, and also the sound you hear when going through teleporters), and has 3 virtually identical "ungh" sounds (when the Doomguy tries to interact with something or falls down).
It's even got a punching sound which I don't think it's used. It might be possible to simply repoint it.
If anyone cares to look into it, here's an example sound file
extracted from the ROM. It's the sound for the barrel/rocket explosion. The last 3 bytes might be paddding, and the total file size is roughly half of the PC equivalent. [EDIT] If the original Doom sound .lmp format is anything to go by, bytes 3 and 4 are the Hz and bytes 6 and 7 are the samples.[/EDIT]
Curiously, I just remembered the Cyberdemon's attack is a... Front facing rocket. I wonder if that is the reason why there was a front facing rocket in the ROM first place.