I like this layout--lots of vertical variation and sorta over-under combat. The slope jump up from the MH level (near the shells) to RL is kickass. I love the slopejumping in Q4 and I really wish more maps would make more use of it. Good stuff.
So. I started looking at the map and thinking about the layout, and I kind of got a little carried away. This has just made it obvious to me that I need to open up the editor and start working on my own stuff again. The following is purely my opinion and what I would try were it my map, and probably a lot more than you really wanted, so feel free to ignore the crap out of it.
I'm offering it anyway, on the chance that part of it might be helpful.
1. This might impact performance a bit much, but a little window to allow seeing (and railing) from RG through to MH would be cool and evil. Here:
I'd also make the RG plat a bit smaller, 'cause I'm an ass like that, and don't forget to either make the blood/acid/stuff shallower, or fill it with fog or something, so it doesn't look bleh when you crouch or die in it. Maybe consider some other effect? Electric or something? The lack of liquid splashy sounds is a sad thing.
2. The map feels a tiny bit big for 1-on-1, and I think it would be much more intense to play if you were to tighten it up just a bit. I'd lose the YA room, and move the YA behind the pillar near RG. Here:
You'ld have to move the HB somewhere too, or else just take it out. Maybe the little nook with the health across from RA? Finally, so there's not just one way out from RG, you could make the passage that previously went to YA room just hook around to the left and pop you up to the new YA spot...
3. Finally, I think RA-->MH is a bit too quick, and I think both of them are a bit too easy to just pick up and be on your way. I would address this in two ways:
a. You could make the RA a bit more difficult to get by forcing a slope jump up the stairs trim to get it (put it on a ledge/crate/something that's just a bit too high to jump up normally). Maybe even put something else nearby that you can hop off to get the height--wall fixture or whatever, but I'd make it so you can't just walk over it.
b. You could make RA-->MH longer and MH more dangerous by blocking off that direct passage. Either just put bars across the RA side, or block it off entirely to help performance. Lose the jumppad up to RL as well. Then put a tele in that dead-end passage that previously led to the RA room. Like so:
Then, if someone grabbed MH, they'd either have to do the slopejump back up (which you could duplicate where the jumppad was), or else take the tele. You could make the tele a one-way, and have it come out in a short passage off the pool o' doom around RG somewhere.
What's the little circular dealie on the floor in the hallway off RG?
Okay, I'll shut up now.