Blackadder said the Crusaders carried only two halfbacks last year and wanted Su'a to put pressure of Andy Ellis and Willi Heinz.
Su'a was a good passer, was strong and physical, and would bring something different, he said.
The coach will be in no doubt about the toughness that tighthead prop Laulala will bring to the squad.
The second-youngest of eight siblings of whom Casey (now with Munster) is the oldest, he fractured his lower back in the ITM Cup but started against Taranaki in spite of the injury.
His recovery will take another two to three months.
Blackadder said Laulala had played two seasons for Canterbury and proved himself to be a promising tighthead, and Taufua had been outstanding for Tasman on loan and then made a real impact when he joined Canterbury for the semifinal and final.
Counties player Tupou was a physical and talented loose forward who would be a real asset, he said.
He would bring something different with a style that sat somewhere between Kieran Read and Jerome Kaino, and could play lock as well as No 6 or 8.
Skipper Richie McCaw will be on sabbatical for much of the campaign and would not be available until after the June tests. When he returned was "pretty unconditional", said Blackadder.
First- and second-year players in the squad will assemble for training on December 10, and the full squad will be back on January 28.
Crusaders 2013 squad:
Forwards: Dominic Bird, Shane Christie, Wyatt Crockett, Tom Donnelly, Corey Flynn, Owen Franks, Ben Funnell, Nepo Laulala, Richie McCaw, Joe Moody, Kieran Read, Luke Romano, Jordan Taufua, Codie Taylor, Matt Todd, Jimmy Tupou, George Whitelock, Luke Whitelock, Sam Whitelock.
Backs: Tyler Bleyendaal, Dan Carter, Ryan Crotty, Israel Dagg, Andy Ellis, Robbie Fruean, Zac Guildford, Willi Heinz, Tom Marshall, Johnny McNicholl, Jeremy Su'a, Tom Taylor, Adam Whitelock.