The switches will aim to provide a number of younger Ulster players with further exposure at Heineken Cup level. There are returns for Stuart Philpott, Declan Fitzpatrick, Niall O'Connor and Rob Dewey.
Speaking about his squad selection, Williams commented: "It was a hard one. There are a lot of guys in the squad who are putting their hands up week after week, and saying they are ready and want to be given a chance.
"Take Chris Henry, he has been asking me for his chance to start and against 'Quins he got it and played tremendously.
"Players like Ian Whitten and Willie Faloon are saying to me they want to have a go. They have really fought hard for their chance to start, and Saturday's match may just be that chance.
"We will look at things over the next few training days and then make our final a decision."
BJ Botha, who missed the Harlequins match due to illness, has returned to full health ahead of this Saturday's game.
But Timoci Nagusa, Carlo Del Fava, Robbie Diack, Cillian Willis and Thomas Anderson are unavailable for selection due to injury.
ULSTER Squad (v Stade Francais): Backs (11) - Clinton Schifcofske, Bryn Cunningham, Niall O'Connor, Andrew Trimble, Ian Whitten, Paul Marshall, Isaac Boss, Paul Steinmetz, Rob Dewey, Mark McCrea, Simon Danielli.
Forwards (13) - Bryan Young, Stuart Philpott, Declan Fitzpatrick, Nigel Brady, Tom Court, BJ Botha, Ed O'Donoghue, Matt McCullough, Kieron Dawson, David Pollock, Chris Henry, Willie Faloon, Ryan Caldwell.