Krijack,
I have a similar situation yours, although just the front of my house has a brick facia. I chose the flangless windows for two reason. The brick being the first and not wishing to cut into the siding to accomodate the flang.
My house has nearly 60 year old cedar siding with hardly any knots holes in it.

If they had cut the siding, I had two choices. One was to replace the siding to cover the flangs. The cedar siding that is on the market today is a bunch crap. Good luck trying to find good clear cedar these days.
The other option was to trim out each window to cover the flang. I personally don't like the look of this.

I watched them install a few of the windows. They are screwed in from the sides so the window isn't going anywhere. I believe they used three beads of caulk during the installation. One on the outside, one in the middle of the window and one on the inside. I've washed them numerous times with a hose had never had any problems with water issues.
I think in your case with the brick, a flangless window is your only option. If installed properly, you've got nothing to worry about.