So, I'm back after reviewing that Parasite information. There are some similarities in the two characters apparently, but not exactly the same. As I mentioned above, Mimic doesn't actually drain the power of the target - he just copies it at roughly 50% power level. He also has no fade rate. Whatever power he copies he keeps until he decides to replace it with another.
I applied some Google-fu to scour the interwebs to see if anyone else had taken a stab at writing up Mimic in Champions, but came up empty. No worries. Not like it's a pressing matter. I was mostly interested from a mechanics point of view in how such a character would be constructed. I think you are on the right track with your suggestion of VPP/Multi-form, and perhaps with the right modifiers his set of powers could be worked out.
If I ever get my campaign going again, I'll likely make a go at trying to write him up myself and see what I come up with. My campaign world is an amalgamation of Marvel, DC, Champions Universe, and my own creations, so I incorporate a lot of different characters depending on the story-line without regard for original universe the character came from.
Thanks again, Hyper-man!