Okay 42, I was trying to think of how to emulate the ability of highlander immortals to absorb powers. So do think this would work? If you use mimic, give it the extras continuous, extra subject, stacking. Flaws: limited (can only mimic powers of other immortals you've killed or whatever, rather than just anyone you touch), tainted (if you emulate their abilities, you also get their drawbacks, via dark quickenings/light quickenings and such).
At first you'd probably just need extra subject x2, letting you mimic/retain the essense of up to 5 other immortals. If you manage to kill more, then you'd need to spend extra power points you earned to gain a higher max kill quota. I mean if you wanted to get crazy, you could start out even at PL 10 with a max of 1000 kills; the most kills ever was Jacob Kell with 665, so I think its okay.
It might even be better to only have a smaller number in memory, b/c that is less things to keep track of. Looking through 665 char sheets would be a little rediculous, basically just keep your best kills and don't worry about maxing out extra subject. Of course with the stacking, maybe just keep track of the total kills granting skill or feat X, rather than their whole character sheet.
You might also be able to take mimic more than once? That would let you mimic more stuff at the same time.