Acoustics and mixing...

For starts, that only deals with equalization and not reverberation or room resonance.

This idea has been touched on a bit here and at some other forums. It's like trying to put a bandaid on a open wound. Inserting an EQ on the master bus may help or it may hurt - it all depends. Surely the EQ is not going to remove unwanted resonant frequencies from the room or any null points or room nodes that may exist. It may tame them a bit but from personal experience I can tell you that if your room isnt treated (which it obviously isnt or we wouldnt be having this conversation, haha) you will be surprised how hard it will be to find that perfect EQ, rooms act differently at different frequencies and at different volumes. I noticed this when I was starting out and I tried this "flat" EQ approach. That EQ curve is going to have to be changed and modified at every volume change to truely give a flat response. It ended up screwing with my mixes until the point I said screw and mixed without it until I could afford room treatments. Just my personal experience. It may work for you and like anything - its always worth a try.

That would teoretically give me the same result as a treated room (which I am working on).

No it doesn't. An EQ inserted, while not being all that bad, is simply a coverup for a larger problem...which is your room acoustical properties. It's like using makeup when you have a zit.

Any thoughts?

I have three at the moment...lucky you...

First Nearfield monitors when placed correctly will negate some of the acoustical problems of a room due to the shorter distance the sound travels to your ears.

Second insert the EQ if you don't have the money to treat your room. Sometimes little bits is all one gets...but you'll always know you are getting a false impression of your room.

In dire emergencies I have been known to *borrow* mattress's, double them over and put them in the corners for bass traps. I have been also know, particularly when I didn't care how it looked, to *borrow* a slim mattress and put a rectangle behind my nearfields.
Not recommended, but then again if you don't have money, but you do have mattresses.....