Engine wise it can probably handle it, I dont see any reasons why not. The only thing that would be new compared to the current situation is assigning slot A to player X before the game starts instead of after.
From the wiki however (
https://www.warzone.com/wiki/Mega_Games):
• No fixed teams: they must either be an FFA or use random teams
• If a custom scenario is used, it must use "randomized slots" feature to ensure that the game creator does not get any advantage over others.
So it appears that by design you cannot assign players to slots/teams to prevent potential abuse...
EDIT:
Sorry for replying so late, only was reminded to look back at this when I saw the feature request 😅
Edited 2025-10-24 21:29:59