Brainstorming for a HL2:DM Level

I've started brainstorming for another HL2:DM level, and this excellent article, "Basics of effective FPS encounter design" from Fullbright has helped me frame criticism of my first published level design attempt, dm_light_industrial. Unfortunately, apparently somewhere in the Snarkpit update, the comments were lost, but one that I still remember was that there were too many dead ends - basically that the level didn't flow, and it was a little generic, which I have to agree with. I didn't really understand the too many dead ends comments, but I think I do after reading Steve's post. It's geared more towards single player map design, but it still helped.
His article gives three basic guidelines:

1. Varied, clustered cover
2. Circular navigability
3. Observability

Summed up, hallways make for uninteresting combat areas and there needs to be more than the binary choice of moving forward or back, with alternate paths that encourage both players to take risks, and the players need to be able to see these choices, and start in a position where they can survey the layout and make their decisions.
Unfortunately, I think dm_light_industrial failed in all three concepts to some degree or another. The map is basically hallways, broken up with rooms at the end, with a few hubs. There are quite a few areas that dead end, and I see now these areas are deathtraps, with no way out and no choices besides fighting your way out, which can be frustrating.
Also, there is no central focus to the level, the one "arena" area is too small and too hard to navigate, with very little cover. It needs to be much bigger, with more hiding spots and cover, and pathways all around the outside of the focal point. I think my next attempt needs to include at least one of these arena areas, a lot more cover, no tight hallways, and a compelling theme. I also need to playtest with other players a lot more, I only got a chance to play it with one person, and just that helped quite a bit.
I'll have to brainstorm a bit more, but I will probably have a rough outline sketched up in the near future. If anyone plays the map and has any more tips, I'd be grateful.

PS: Steve Gaynor's "make cool shit and show it off" entry is also worth a read.