i was reading the current topics, as usual, and this hit me. to make the x-blade, you need a heart of pure light and a heart of pure darkness to fight, forging the x-blade. well, vanitas already provides the heart of pure darkness. but ventus is injured and can no longer fight to forge it. assuming vanitas comes back, kairi would serve the role as the other half to forge it. why? because shes a princess of heart, so she has a heart of pure light. and in BBS, they established that kairi can wield a keyblade. so, this is what i picture. kairi learns how to weild her keyblade(no matter how much i despise the idea), and vanitas shows up with orders from terranort/MX to forge the x-blade. kairi fights hard, but is obviously no match for vanitas. the x blade is forged, and terranort has his x-blade.this, in my opinion, describes why they went through with the hideous idea of giving kairi a keyblade, so she could fight hard enough to forge the x-blade.