Doom is not the venue for hunting for hidden buttons.
You want to create a convoluted series of events so that players progress through your creation? That's nice, but check to see if you're in the right game first. I use a teleport to end one hell-ish level, only to find myself standing on a toilet in the next one! The only challenge brought forth by the maps is having to force the player to look up a walkthrough to progress through the levels. The order of levels is completely out of whack, The build-up in enemy and weapon progression is too slow, and what at first appears to be connective levels (the start of the next level sharing traits with the end of the previous one) quickly falls apart. Requiem is considered a classic because it did some truly neat things with the Doom engine back in the 'early days'.
While there are some clever sections here, I gave up at about Map08 or something, I just wasn't having fun with this one.
Long-ass corridors and huge chambers, but then an almost anal approach to key- and switch-hunting. Remember when you were a kid and you were drawing a house, and it would be disproportionally huge? Eternal Doom is like that.