Punishing lurkers in a 50 player game will be harder though (which is why you've made the distinction between lurking and afking I guess). Imagine, in a 38 player game, all 38 players being really active and posting 5-6 times an hour. Way too much of a headache. With *50* players lurking is pretty much a good strategy for almost every role - a Town PR can bide his time and get more results, a Mafia can hide amongst the hubbub, a neutral can work from the shadows, and even Citizens can lurk until they see an opportunity to review their scum-tells/claim a PR/take a bullet.
50 players, inventory systems, multi-votes, levelling up... I really hope it's worth it Yayap. This is one game where I'd hate to be Town, even a PR, because I'd be overwhelmed trying to keep up with the day chat.
I suggest you add in a rule where, if you cast a vote without putting up a correct tally alongside it, you will get modkilled instantly with no exceptions.