Eh, I'd say for now death or serious injury would be a bit much, and might detract from the abilities and circumstances of characters in the future. Death will certainly happen, but it is my opinion that on the first mission it'd be a bit much, especially given that the mission is a capture mission. Of course you can still use this as a chance to show Nathan's dark past when it comes to these fights, just hold off on the killing and/or maiming...for now.