As much as I love the idea of having Authentic Classic Matches. I just can't see it happening with the limited time and funding as EA are not currently backing the game.
I think a more realistic option would be to introduce 20 Unlock-able Legends after winning the World Cup with that country. The players could be drafted into any team or create your own team.
My proposed Legends would include:
Wales: Gareth Edwards, Jonathan Davies, JPR Williams
England: Jason Leonard, Jeremy Guscott, Martin Johnson
Ireland: Keith Wood, Willie John McBride,
Scotland: Gavin Hastings, Ian McGeechan
Aus: David Campese, Michael Lynagh, John Eals
NZ: Jonah Lomu, Sean Fitzpatrick, Zinzan Brooke
SA: Joost Van Westhuizen, Francois Pienaar, Os du Randt