I downloaded it and took a quick look, haven`t played around with bots yet.
The layout does seem to be large-ish, but not really larger than most duel maps these days (compared to dm6 / ztn). Maybe more open, perhaps. I agree that in some ways it might be more suited for casual dueling, although it`s not bad and it could be fun for small FFA`s or 2v2 TDM.
The striking issue is the item placement. The RA and MH are very close to each other. Yes, the RA is backed up next to a wall where you can be pinned down, but if luck goes in your favor you can grab the RA and MH very quickly, and a YA as well, giving you a stack of 150 / 200 in perhaps less than 5 seconds. This makes it extremely difficult for someone to regain control in duel, as there is only one YA in which they can use to regain control if the aforementioned scenario were to occur.
What I would do imo:
- Remove the YA which is in the same room as the Mega Health.
- Move the YA in the railgun room to where this 25+ health is in this screen:
http://dl.dropbox.com/u/27277779/q3dmp23_screen4.jpg. Then, swap the positions of the Mega and the PG. Mega would be in a low corner where one can easily be ambushed then.
- Move the RA to where the YA in the RG room was.
Also, one architectural issue I noticed:

That upper walkway seems odd. It`s an interesting idea layout-wise but from a physics perspective it feels wrong imo. Being so thick (therefore having more weight to support) and only being held up by it`s connections, it seems like it could collapse very easily. The red markings show where I would place columns. Not only would it make it look better (imo) but it would also improve gameplay in the sense that people can use columns to take cover from fire. You don`t have to make them super thick, maybe at least 32 units wide would do.
Overall it`s pretty good. Just needs a few item tweaks and some other things, but it seems like it could be really fun to play. Jumping off the slopes in particular is fun in CPMA. gj!