You should be thinking about the starting XV and bench that will defend the Webb-Ellis trophy in 2023.
You should be considering the age of players and the likelihood of them lasting until the RWC. If it was me I'd be discounting 30 and older . . . so out of my thinking go Beast, Duane, Willie, Flo, and Fats.
Those are the only players I'd consider replacing at this stage. The rest of the players in your match 23 are the magnificent warriors who won the last one and gave the country such a massive boost. You'd have to have the cranial capacity of a ping pong ball or the rugby acumen of Omlet to even consider going into the next RWC final without as many of those players as are still one their feet in 2023.
So you need a loosehead prop, a number 8, a fullback, a bench flanker and a bench utility back.
Who would yours be if you were picking your first Springbok squad (assuming no limits on foreigners which seems inevitable now)? Mine . . .
1. Ox Nche
8. Dan du Preez
15. Damian Willemse
20. Jean-Luc du Preez
23. Curwin Bosch
Kitshoff would take over from Beast and I'd cash in a free quota card and bring in any one of the young promising black looseheads. On the other side of the scrum I'd be choosing between Malherbe and Koch for the #18 jersey with Nyakane my long term hope for the #3 jersey.
I know I'm in a minority when it comes to the Du Preez twins. I make no apologies for selecting them both but go ahead and add your own choices. Note that I'd be thinking Pieter-Steph back at lock in the longer term.
I prefer Damian Willemse at flyhalf but would back him to shine at fullback as well. It's not a problem area for us and there are any number of talented youngsters who could prove himself in the next 4 years . . . Tyrone Green, Aphelele Fassi and Curwin Bosch to name a few.
As for including Bosch as my utility back, sure he has a weak defence but that can be inproved. He offers so much else it's worth giving him a shot. Also, if you're doing a like for like replacement for Frans Steyn then Bosch gives you similar versatility and similar distance with the boot. Frans and Curwin are two of the sweetest strikers of the ball out of hand that I've ever seen . . . certainly since Derrick Hougaard.