hmm... interesting...
Ok, i'll bite...
Buffy - Melissa Joan Heart (Younger days obviously)
I can see MJH doing a feasable Buffy, she's got comedy timing down pat and can do some pretty serious roles when it comes down to it
Xander - Joshua Jackson (Younger days again, think Dawsons Creek era)
I can see him doing Xander pretty well... he's got the sarcastic humor down but can also pull off some dark roles along with tragic romance (See Fringe if you don't believe me)
Willow - Bonnie Wright
Possibly a perfect Willow, cute redhead who can do bookish and nerdy at the beginning but really grow up to be a perfect flower...
Giles - Jason Carter
One of the few people I can see as Giles aside from ASH... he can do bookish and old style, but had a darkness underneith that can really shine through.
Angel - Tom Welling
One of the perfect 'brooding dark hero' actors, think he'd do amazing as Angel, can pull of dark and mysterious while still trying to act like a hero.
Cordelia - Tiffany Amber Thiessin (Younger days again, think Saved by the Bell era)
The rich queen of the school, perfectly pretty and pristine to look at, but with hidden depths for people to find.
M