Another way to do it is instead of shifting the XP around shift the spotlight.

The simplest example is the Leader who gets XP when their plan lets someone else shin. ... Of course I'm not sure how to define that in game terms. Let me try the Big Guy, instead of getting XP for defeating a big enemy you get XP for defending an ally or buying time for some other part of the plan to be completed. And an idea for a smart one popped into my head.

When you give another PC advice on how to approach a situation, roll+sharp:
On 10+ they hold 3 and you gain 1XP if they tell you how it went later.
On 7-9 they hold 1.
On -6 [something bad]
They may spend hold one-for-one to: [options]

So that will need some additional work but I think the basics are there. You get XP for making the other characters look good in a way that is appropriate to your character. Hopefully playing off both the archetypes and the group dynamic as you want.