Its not even 3 days to learn the new system for a number of them, as they are away on international duty until Thursday/Friday and Saints will travel to West Brom on Friday.
You want the players to learn to play a system they've not used before in the next 3 days? That is quite a risk!
I doubt Puncheon and Rodriguez would be effective wing backs anyway.
As he hasn't managed it by the age of 27, I wouldn't get your hopes up. He is a good Championship level left back and is out of his depth in the Premier League.
Clyne is too old to play for England Under 21's anymore. Players born on or after 1st January 1992 are eligible until the end of the 2015 UEFA European Under-21 Football Championship. Clyne was born 5th April 1991.