Fusion suit Samus is the one thing that has always stuck in my mind as the perfect choice for a "dream" cosplay project. It will be awhile before I am able to afford such a costume.
I would want to be sure to have a working arm cannon, which would use a combination of things.
Something like this, with lasers and other things (such as a charge of compressed fog which emits in front of the blast zone, so the lasers can illuminate something). I'd want to be sure to design the arm cannon so that it can be pulled with fingers from within to easily charge, and letting go would fire.
I'd also want an HUD with LEDs on the face visor, and multiple LEDs and perhaps inflatable yellow portions which would glow, as power is charged.
I'd probably want to add countless amounts of detail to make it interesting and to make it seem super special.
Maybe one day.
EDIT: I am also open to the possibility of designing my own type of suit, and not use the fusion one.