So! Gave it a proper run, and there's a fair bit to talk about here.
One thing that occurred to me after I finished playing the map was that a map that emulates the styles of two authors - a collaboration - also begs the question as to how those styles were implemented and in what sequence, as undeniably there are many ways in which this could happen. Did American create the layout and then abandon the map leaving Sandy to piece everything together? Was it the other way 'round? Or perhaps Sandy proposed an idea to American, who textured a series of rooms only for a dissatisfied sandy to jump in take hold of the reins! How, for this matter, do we suppose Dead Simple came about?
The map feels to me like less a "collaboration" between the two designers and more of a disassociated fusing together of styles to create a map which showcases the different mapping traits of Petersen and Mcgee (in places). This doesn't say anything about how successfully their aspects of design were implemented, of course; just that they don't come together in a way that would indicate the map had "evolved" or progressed between designers in stages. There are certainly a few noticeable traits in here that are worth pointing out and developing, but the first point is the one that I think needs addressing the most!
On to the positives...:
On the American front, there's a rather "interactive" element in the form of a raisable/lowerable floor, a returnable bridge, and one or two instances of bars or lifts that are switch activated rather than manually up front. The Focus (coincidental map slot) features on/off lights and a crusher window, The Crusher features its namesake activated by a modest switch, and The Gantlet features a couple of switches meant for remotely activating nearby objects and tricking the player. The list of examples is considerable, and critically they are often quite trivial or small scale interactions/actions. I think you've got this aspect down pretty well!
The closet traps are pretty McGee as well, with the sergeants behind the corridor window near the start as well as the instance near the exit being good examples.
One thing I think would have helped immensely on a similar front would be focusing more on localized, set piece fire fights/encounters as opposed to (or intermittingly in place of) a more unrelated scattering of monsters seen here. Since this is a map with a pretty compact structure we can't really compare it with maps like map03, 06 or 14, but encounters of the kind seen in maps 02 (red key/blue key/exit points) and 22 (baron>chaingunner trap/first emerging into the outdoor intersection), which features encounters of the sort described mingled in between a distribution of monsters similar to what you've got here, would be great examples to study assuming you're going for a more American than Sandy map.
To me the layout only seems American with it being a linear map featuring one corresponding object/door to each key, and perhaps the way in which the player progresses through the map. Unfortunately I cannot really vouch for it seeming a sandy layout either as the player doesn't really come across any areas that are provided their own concepts and neither does the map demonstrate some sort of overarching concept (examples of the former would be map09 in the context of a more linear map like this one where the player revisits some areas, map21 or map27. Examples of the latter would be map23 and map24).*
The last room is detached enough that it could be either Sandy or American, but isn't committed enough to an idea or orchestrated/arranged enough to be either.
The geometry of the map is clearly bending toward Sandy a lot more, and I think you're on the right track with it so far, but it suffers a similar problem I think as the texturing. Texturing - and visuals in general - take a back seat to conceptualization and fun with sandy, so once again without any real overarching concept to this map it seems odd and rather unlikely that he would commit himself so much to the task of creating such elaborate contrast and variety without a supporting concept.
Megalyth's Passage to Exile works with this sort of combination I think because it accommodates the idea of the merging of worlds. The texturing therefore takes a front seat next to fun/gameplay!
Similarly with geometry, Sandy will only really tend to it where it counts, otherwise mapping out whatever the hell is necessary just so that it allows for the concept he has in mind to come to fruition.
Holy text, Scatman! Looks like I've gone overboard.
Overall, I would say that it doesn't convince me of its being an id creation, but it does clearly offer some well honed examples of McGee's mapping traits in particular, which is just as well because its his maps you were aiming to draft ideas from! I think that if you want to continue with this map I would focus entirely on its becoming an American creation - perhaps starting by eliminating some of the non-orthogonal geometry within larger rather than connecting areas - and otherwise try and imagine the map more as a literal "collaboration" instead of the simple merging of observed mapping traits.
Did I say good job? Good show :D
Feel free to disregard everything I say and storm back to the drawing board with your own ideas, if you disagree! :)
* Some maps like map08 and 13 marry the idea of an overarching concept or gimmick with a series of concepts that act independently of each other.