I think the Doom Bible was talking about many small maps, not few big ones

[Blastfrog]

I suspect that the original concept was that each building's different floors were meant to be their own maps, as opposed to mere height differences in one map as the alpha maps were. The elevator concept carries over from Wolf 3D quite directly, it seems.

Smaller maps would have both fit into a smaller memory requirement than the final game (they were originally targeting 640kb IIRC) and would have also made loading times between maps much quicker, which is desirable because map loading would be rather frequent.

[Hoodie]

At least Tom Hall got push walls...wait hold on

[Maes]

So Doom was meant to be nothing more than a Wolf3D reskin? Meh.

Let alone that 640 Kb was already pretty marginal for the original Wolf3D as it was.

[Da Werecat]

Maes said:

So Doom was meant to be nothing more than a Wolf3D reskin? Meh.

A Wolf3D reskin with an Actual Story. It makes all the difference in the world!

[Blastfrog]

Maes said:

So Doom was meant to be nothing more than a Wolf3D reskin? Meh.

Though probably flatter feeling than the final game, I have no doubt that they would've wanted to still have height variation within the floors.

Hexen-like open-world retaining level states upon return and Duke 3D level of detailed interactivity would've certainly made it more than a mere Wolf reskin.

Maes said:

Let alone that 640 Kb was already pretty marginal for the original Wolf3D as it was.

According to the post-mortem, the intention was to lock the player in a small room while the other level loaded.

I imagine that they'd try to use as little assets possible at any given moment, but would frequently switch them out as you moved from area to area.

[Maes]

I doubt they could have gotten away with marketing something like that, when the competition wasn't exactly sitting doing nothing.

Maybe as a stopgap title, while they worked on a "Doom+" type of engine, or even straight to Quake. But without Doom, I doubt this approach would have gotten them enough funds to continue development. Maybe only if they stayed under the wing of Apogee (but then they might end up with ROTT instead).