Thanks to some help from the awesome folks at bfmods.com, I was able to modify the main BF1942 objects archive, adding 'game.setMinNrOfPlayers 0' to the 'objects\Soldiers\common\CommonSoldierData.inc' file. This stops the unwanted restart behaviour in all maps, since the modified file is loaded on every map load.

Please check it out and let me know if it's working as expected.