Imo current layout wastes good design. Look:

To make my point even more clear:


When I am in the caves, I can't say where I am without minimap, and I can't say to my team members where I am at all. 360 degrees - same texture. I have some ideas and suggestion how to solve this problem.
First of all - a happy story. I read once a book about screenwriting. The team of screenwriters had to write screenplay about family and white pony. They were unhappy with their script. They could not fit whit pony into story. So they started to rework material over and over. To fit this damn horse. After few months they were extremely happy with story - they have achieved what they wanted. And one of them asked - where is this white pony in our nice story? And they have realized, they forgot about him. Thanks to that, they have written good story.
What teaches us this story? That sometimes it's better to cut off a large piece of our work and start over. Because we are sometimes in dead end without even knowing it.
Gloom takes place in some jungle/cave environment. Obviously, you can rely on caves only. Now you do and look - labyrinth. What I propose is looking outside of the box.
Caves are great idea if you use all potential and add some other things, that will make them video-game friendly.
Have you thought about water? It's common there are lakes underground. You could add small lake with a small island-alike thingy in the middle. With circle jump ppl would have opportunity to go on shortcut.

That area would be more open-space, less claustrophobic. If you have added there some different light, it would became nice orientation point!

There is a map, ut4_guerilla. It's very randomly created, but has nice idea. Water canal. And this water is shallow. You can't swim there, but you make a lot of noise traveling there. This little lake on Gloom could have a shallow water. No stupid problems with flag falling down there too deep or bomb.
Think about lake.
If we speak about lake, why not go further - river? If river - bridges! They can be "normal" bridges, or more alike fords http://en.wikipedia.org/wiki/Ford_%28crossing%29

OMG! Another TWO orientation points! Not to mention, that you can separate more areas of your map, but add sneaky shortcut, if some one is ready to go deeper into river and emerge on the onother side:

Just one that kind of shortcut, call it "Devil's Throat" - 4th orientation point. And if you plan it carefully, river can lead to village!

Let's go further.
If you have houses/shacks - it means that ppl live there. Why You won't use it for your own evil plans. Look:
http://1.bp.blogspot.com/-cAWYSTizjTo/T ... an%2B1.jpg
http://1.bp.blogspot.com/-AOFyjh20sfw/T ... an%2B2.jpg
http://1.bp.blogspot.com/_yqsQcxWk4iw/S ... 282%29.png
And so on. One village can be shacks/that kind of houses - that would be native ppl with Pocahontas as their leader, and onother side could be slavers/drug dealers camp:
http://gurstin.com/trips/2008/Honduras/IMG_8951.jpg
Put there a jeep and some weapon crates and you are done.
Moreover one last thing. You could transform this little hole (almost unnoticable)

into THIS:
