I'd probably point out to my player that the only reason the role is called "Leader" is because "Support Monkey" didn't test well with the focus groups...
If you're just talking about a character who has general leadership abilities - inspires the crowds charismatically, inspires loyalty in followers, can convince men and women to lay down their lives in her defense, etc. - then I don't see why you need to dip into a "Leader" role class at all. The "Leader" roles are all about the particular combat tactic of buffing other characters, that's all, and you don't need to be a "Leader" to lead people.
Now if what you're REALLY asking is "how do I make an arcane character who can be an effective multiclass arcane striker/support monkey" - I dunno yet. I imagine that eventually there will be an "Arcane Leader" class that might fit easily into what you're talking about. If I had a player come to me with a great striker/support monkey concept I'd probably work with him to reflavor the warlord support monkey powers to make it fit with the concept - but that's only if the player really had a good concept and wasn't trying to cherry pick stuff from the warlord that would create weird synergies to give him some kind of bonuses he wouldn't get otherwise.
(As an aside - this is why I hate that they named the role "Leader" instead of "Support". Sure Leader sounds sexier than Support but using the term "Leader" is going to make people think that the wizard can't be a party leader, or the paladin can't be a leader, or that the guy who picks the cleric automatically has to be the "party leader". Which, frankly, generally doesn't happen in my games. The support guy taking the cleric or the bard is rarely the guy who ends up standing in front of the village elders and apologizing for the way the rest of the party trashed the town square the night before...)