We don't know if Ca or Wieskamp will get those two-ways or even get regular roster spots. I wouldn't rely on using the two-way slots to solve the roster issue.
I understand why you could say the Spurs could just trade up. It's intuitive, but the data we've seen for multiple drafts suggests that teams with multiple first-rounders don't get to package them to move up in the same draft very often.
In the last five years, I've seen two examples:
2019 -- ATL traded 8, 17, 35 and a future first to NOP for 4
2017 -- POR traded 15 and 20 to SAC for the rights to 10
I was going to stop there, but seeing SAC in a trade reminded me of the trade the year before:
2016 -- PHX traded 13, 28, future second and Bodganovic's rights to SAC for 8
The Collins trade in 2017 is probably your best comp, given that it was the only straight trade-up that didn't involve future picks. Maybe it could be worth it, but this trade, and indeed all of these trades combined -- aren't the usual results. You should look up those drafts on Wikipedia to see what teams with multiple firsts usually did. Most of them either took all the players and dealt with the roster glut we've been talking about, or they just took salvage value for the picks. It's not the worst thing if that happens and they get a good deal, but I would at least assume they'll make the picks.