HypersomniacLive: I still disagree with the rest, even for an all vanilla setup; it may be good from the replacement's side, and perhaps help with the shortage of subs we face, but it'd still interfere with the game state and progress. Not sure if you saw my post #3619, but I think that is a good example as to why not to do it this way.
The larger question may be "What method of handling replacements is less disruptive than a mod-kill?"
Perhaps the solution is "Announce that Existing Player X is going to be replaced" without announcing who is taking their slot. Each team can make plans based on who is likely to show up, but the player isn't removed from the list without having any effect on the game except reputation (and threat of new eyes). Scum can be aware that "if we NK the slot being replaced, then the specific replacement player might or might not show up later".
That does leave open the question of whether to announce when the replacement will occur, once a replacement is in hand. Tell the replacement in question that they'll be in the game soon, but don't pass them PM data until they can start posting somewhere?
If you don't need to preserve replacements as long as possible, then just toss them in the game pronto. You'll occasionally lose one to NK before he does anything, but it is a straightforward solution. If you're already low on replacements (as is usually the case for us), then I don't see a way around at least one team taking a hit unless the replacement naturally happens during the early/mid day.
HypersomniacLive: Town, actually lies a lot more than you think; there are a number of players here that don't fully embrace the principle that town never lies.
And certain townies do self-vote here.
Having done both, including self-lynching a town PR out of pique, I can vouch that these are true statements.
