Here are our options and consequences in order of best possible town outcome (my opinion):
1) we lynch an active player who flips scum- We will start D3 at worst maintaining our town majority (3 scum/4 town) and at best the scum kill each other at night and we are all of a sudden have only one remaining scum. Also, we will be able to examine his reads and learn stuff from that.
1) we lynch a lurker who flips scum- Again, town majority, same chance that we end up with one remaining scum (not likely). Now, since this player was a lurker, we have fewer reads from him, but that can be a good thing since fewer reads mean (hopefully) more focused reads and we can determine at least who was NOT his scum partner. I don't think a scum!lurker would ever read scum on his partner (except maybe on a lynchwagon, but that can't be the case right now since we faust was town), while an active scum player might do so.
3) We lynch lurker who flips town- Well, this is bad news for town. But not terrible. At best we will still have at least 2 scum with 5 town. At worst we will have 4 scum and 3 town. Now, 4 scum and 3 town isn't as bad as it sounds, since scum will now really be trying super hard to catch the other scum team, and it could very well result in a triple-scum death out of D3/N3, but still not the place that we want to be.
4) We lynch an active player who is town- This is just bad news all around. We lose an active contributor. Same bad situation for town as described in (3). I really hope this is not what we do.