If Tim Russ dyes out the grey he will look exactly the same, especially with a little makeup.
Janeway.. sigh. The big qualities would be:
The warmth and her quality of seducing everyone into doing what she wants.
The directness, the barking out orders like you mean it. No one like Elizabeth Weir in SG:A who delivered all her lines like a terrified flower.
It's the ability to bark and seduce in the same character we need.