Here's something a little crazy. It breaks the concept of roles, but it should work fine in an experienced group.
Use the rogue as your starting point for class features, but replace sneak attack with hunter's quarry.
Give him proficiency with all military weapons.
Give him Ritual Caster as a bonus feat, but no rituals to start with.
Now, with powers things get interesting. When he takes powers, allow him to choose from any class, with one caveat: he can only take a second power from a given source if he needs to add another power and he has no more power sources to choose from. Even in that case, the power must come from a different class than the earlier one from that source.
For at-wills, he must take one with the implement keyword and another with the weapon keyword.
This gives you a character who is sort of a striker, but who dabbles in everything.
The interesting thing is that, since the classes are balanced across the board, he isn't strictly better than the other PCs. There are some pitfalls - the restrictions on classes and power sources is there to stop him from just taking all wizard powers, while having better HP and AC than a wizard.