Shit happens. Most of the hostkills happen for that very reason. It's sometimes unavoidable, but it's up to the host as far as what to do. Either way, it can result in a ban.
Introducing someone new to the game goes against the flow of it. Every player should start and contribute from the same point. You're basically saying that the new guy didn't have to post until the point he replaces someone, adding nothing to the game and having no impact on it or it's players prior to him joining. Just because you're avoiding hostkilling someone doesn't mean you're actually balancing anything at all.