@meganoth
I was referring to your whole first and last paragraphs primarily, which were laden with sarcasm and essentially calling the ideas I support "lazy design" in a mocking way. I took it as very combative.
I tried for "eloquent" but failed.
The "lazy design" is a misunderstanding, I called (probably in a too cryptic way) designing to ONLY prevent people from doing something in the underground a lazy design. Hopefully my example makes more sense now. I wasn't refering to the air vent solution at all (I even called it appealing in the same post)
And I know you don't think it should be "designed lazy" either, because you propose the air vent idea exactly because you think it is fun and regard the gas mask idea as inferior for that very reason.
But differences aside, you do bring up some good points. I'm also a huge supporter of both sentry zombies and breadcrumbs, it's just that I've been primarily supporting ventilation. If you combine these suggestions what you have is a system that serves as a technology gate for reaching 100% safety underground as well as active underground threats (zombies following you underground from your entrance).
Yes. But do sentry zombies really fit in there. Isn't the central idea of that that they wait above and don't follow you, almost the contrary idea to breadcrumbs ?
As another user suggested, your vent could also generate heatmap which would bring zombies to the vented location (provided a player is present in the chunk) similar to the way screamers approach forges. Then through the breadcrumb system they may wander and try to find a way to engage you, or they may start digging - forcing you to build defenses for your intake/exhaust system. In normal situations, maybe there would just be a few zombies near the entrance to your mine and that's it. Maybe there would be "events" like the wandering hordes where zombies would follow the breadcrumb trail down into your mine once a day or so. Not too much to make it frustrating to mine, but enough to keep the player engaged underground. And of course on 7th nights you'd be automatically hunted which would make hiding underground astronomically difficult if not impossible without a significant investment in defenses. From a base-building perspective it could be fun and interesting to develop systems to establish yourself underground. Maybe it would be too complicated for the average player (or rather, too complicated to communicate to the player) so a simpler solution like diggers and breadcrumbs would have to be employed. That's ultimately up to TFP.
I'm fully on the same page with you here, it doesn't matter that you primarily look forward to design of the air vent system and I to the zombies crawling through it ;-).
TFP's difficult job is to make certain that there are no easy exploits here (building the vent opening far away, ventilation working through hatches, grills or half-blocks). Not only because it is one of the goals but also because I don't want to play like an idiot just so zombies find a way underground. Especially in co-op it just doesn't work to say to your co-players "Okay, lets not put a hatch on this opening even though it prevents zombies from following. We don't do that because we roleplay idiots now so we get zombies underground.". Ultimately I suspect at least one digging zombie is still a must, even with air vents.
One of the big perks of a ventilation system IMO would be the necessity of vent intake and exhaust in PvP scenarios to discourage players from having a cheesy underground safehaven for their bases. Players could still attempt to conceal their exhaust but it would give detectives some form of telltale sign that a base is in the area. In the past, the sound radii were large enough that you could stalk players using sound. Now the map is much smaller but the sound radii are far too small so the chance that you encounter another player through anything other than sheer luck is minimal, which isn't as exciting from a PvP standpoint. Don't worry, I know the game isn't being made for PvP, but that's how I play the game so it naturally plays a part in my perspective here. I think there are possible solutions that could be fun from both a PvE standpoint and a PvP standpoint. And maybe ventilation isn't that solution but out of the choices here it's my favorite one.
IMO ventilation is definitely and undeniably a feature (no, FEATURE) in PvP while a lot hangs on the specific implementation in PvE whether it is a success. I don't mind PvP players getting some sunshine too.