For me, using elevated killing corridors like Jawoodles designs have worked well by adding a ladder in the safe hub that leads up to the barred "ceiling" of the corridor. Walking along the top of the bars and crouching down lets us pick up bags in the corridor, though it does expose us to vultures. Some bags drop down onto the ground, though, so instead of building the base on the dirt ground, we built it atop a basement with more bars as the ceiling (which then is the floor for the pillars for the elevated base) that we can go down into from the hub as well, and it allows us to pick up bags from underneath them as well. It's safeish - gotta be careful with the timing and the types of enemies as you do not want a cop or a demolisher to blow up on the barred ground while you're down there underneath them.
I unfortunately don't have any clips or screenshots of the design, and we lost that world when our buddy, who was host, deleted it by accident.
Alternatively, if you're efficient killers or don't have the spawn rate turned up to max, you can go with an interconnected series of killboxes, and simply wait with killing the Zombies until they're right against the walls. You can easily grab the bags on the outside if you build the walls thin enough; either half blocks or plate blocks.
Killboxes for us are 7 by 7 (or however big you want them, but I don't recommend exceeding 10 by 10) cages of solid walls with open gaps at chest and head height. So 7 wide, 7 long, 3 blocks tall square hollow on the inside with a ladder in the middle leading up to the top of it, covered by a hatch. Middle row of sides are "open" for 5 blocks width, where the only block placed in them is something like a single pole, rod or small square bar - something that has the same amount of health as the other fuller blocks, but doesn't block your view or aim, and which means the Zombies still need to break 2 blocks on top of each other to get through. The entire top of the box is filled with prison bar blocks to allow for shooting up at vultures and any zombies that may stack and make it up there.
Build a couple of these with about 25 blocks of space between them, and connect them with a single block wide bridge leading from box to box at ceiling height (3 blocks) - but make sure there's a 1-2 block long gap between the bridge and the ceiling that you have to jump; you don't want the Zombies crossing over after you that way.
If the box you're in is taking a lot of damage and it's happening too fast to repair, or a demolisher gets shot wrong, or for whatever reason the Zombies make it through, it's as simple as going up the ladder, onto the ceiling, jumping across to the bridge leading to the next box, crossing the bridge and then going down into the next box through the hatch, and then rinse and repeat. Material heavy, for sure, but for efficient miners/crafters, it shouldn't be an issue by day 14, or maybe 21. Friend and I are on day 11, and we've already got 2 boxes upgraded to concrete with another 2 to be ready by day 13.
It's also a safe way to ensure you gather most, if not all, of the loot bags.
Storage wise, if you're grabbing all the bags over such a long period of time and find yourselves lacking inventory space, I can recommend digging 2 or 3 blocks down into the ground inside the boxes, place a storage crate at the bottom, and use brief lulls between groups or waves to deposit loot into for safekeeping. Being a single item underground, inside the killbox, means it'll be out of harms way and not targeted by zombies; anything less than a demolisher blowing up inside the box should not damage the crate.
But understandable. I hope you have success with trying out this new stuff 
