Hey, you don't need to preach the differences between Samus and Dark Samus to ME, okay? I know the differences.
All I'm saying is that it's possible to ignore a few of them, make Dark Samus a clone, and not come out too far behind.
For one, the no contact thing needn't be such a big deel. Samus never, ever hits anyone in her games, she shoots them, yet in Smash she attacks directly all the time. Call it artistic license. DS can do the same, and most likely WILL, be she unique character or clone.
Besides, a few key moves can make all the difference. Look at Captain Falcon and Ganondorf. Ganondorf has a different walking animation, neutral A moves, and a different Fair. Change Samus' walk to a float, and her neutral A and Fair to a phazon attack (no contact, of course) and you've got yourself a whole new animal. Adding blue phazon sparks to the rest of her attacks would just be icing on a sweet, sweet cake.
I'm not saying it's the best case scenario, but be realistic. Dark Samus can't beat out Ridley, and being the fourth Metroid character is going to be hard, even harder now that we know that being an assist trophy is an option. If Dark Samus is to be playable in Brawl, I'd say that being a clone is her best shot at the title.