The Maintenance Tunnels are the scariest area in the game: dark, claustrophobic and with a really fitting creepy music. So, having them randomized too would make them even worse than now! (that's a good thing, since this is an horror game... )
I don't know how hard it could be to generate them but apparently SCP-860's forest will have a completely different seth of paths everytime you start a new game, so even the Maintenance Tunnels could have a way of getting randomized. They should not be that huge, just a bit larger than the actual ones (but with shorter and a bit, but not so much, intricated corridors...) or they would transform in the "Rage Due To How Easy You Can Lost In Them-Tunnels"...
And an even better thing could be having more elevators connecting more parts of the Heavy Containment Zone, maybe the area could be created as a 4th zone that can spawn only in the HCZ: the game would initially place a "indicator-object" (that should indicate the game the area where it should use the rooms for the Maintenance Tunnels) at the same height as the other zones and start creating the paths in the area indicated by the indicator, then it could teleport all the rooms to a given "y" coordinate placed really down below from the ground-floor where all the other zones' rooms get placed and place the elevators under the elevators on the ground-floor. But I'm just thinking, I don't know how hard to do it could be... (I don't even know if that CAN be done! )
The tunnels' appareance could be exactly like the actual Maintenance Tunnels, but with two long and thin pipes placed in the two "angles of the roof" that would travel the entire area, these pipes could have some little cranks placed with long distance intervals between them.
As usual, SCP-106 would like to appear in them...

I have some ideas for possible rooms:
-Standard corridors
The standard corridors, they could look exactly like the actual Maintenance Tunnels (except for the two long pipes). The possible shapes could be:
- Straight two-way (the most present)
- Three-way
- Four-way
- 90-degrees angle (the rarest)

-Standard two-way corridors variations
1) Corridor with a damaged pipe
Gas could get sprayed from one of the two pipes (it could appear when the player approaches a crank, so it could work as a jumpscare too...), you would need to interact with the crank near the damaged point to stop the gas and continue. If you touch the gas (even with the GasMask or when crouching) you will get badly injured and most likely killed...
2) Corridor with a grate on the ceiling
There could be a square-shaped vent on the ceiling where SCP-173 could spawn if you are unlucky; the screen could get black as usual and then you see SCP-173 with a grate near him on the floor. There could be many of them but only one will have the event.

-Dead-ends variations
1) Empty dead-end
A wall that ends a path.
2) Dead-end with a door
You can find a door with no button/keycard slot/keypad near it in the actual Maintenance Tunnels, it could be used as a variation of the standard dead-end.
3) Little room with SCP-500-1
The room with SCP-500-1 could be used as a non-common dead-end room (it could spawn only once...)

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What do you think of that idea?

This could be interesting, maybe the tunnels could be loaded like how the pocket dimension is currently, just without the sickening screen effects.

I like this idea! Man, I HATED the maintenance tunnels, since SCP-106 is GUARANTEED to spawn and SCP-173 has a chance of spawning!

These are two images that could be useful for getting better how I think they could be generated: Each square in the images is 1/4 the size of a standard room (both lenght and widht of the pieces used for the tunnels are half of a standard room's ones...), the area where the game can place the tunnel pieces could be rectangular, as I specified the exact size under the images. Different elevators will take you to different places in the facility.
That means that you would probably get back inside them more than one time to reach a different section of the H.C.Z.; that if there are more than two elevators, obviously with only two of them you have no choice on where to go...

Since I read my firt post and I had trouble in understanding what I wrote ( ), I think that now it should be easier to get what I mean...
LOL, I don't know how to speak anymore...

There's now a similar mod which randomly generates the tunnels with a set of hallways and maybe some special rooms in the future. Don't have the link, it's in the modding section.

http://scpcbgame.com/forum/viewtopic.php?f=11&t=3659 is the link, juan made the mod.