Here are my rules for this team, and the reasoning for them.
This isn't the first time I've played D2, of course. I previously made Hardcore Guardian with quite a few solo characters. But eventually I came to get really loose about the guidelines of legitimacy, with item twinking and reuse, imbue and hellforge rushers and mules, skipping ahead with the -act5 parameter and even by giving them waypoints. I wanted to cut off from that and get back to basics with a new project, and these are the rules I decided on for that.
Why such restrictive rules? In general, because each restriction also covers the cases without it. If I can do this without mods (like ladder runewords), I could in principle do it with them. If I can do it with limited item carrying capacity, I could do it unlimited. If I can reach seven Guardians without respecs or twinking items to younger characters, I could do the same with respecs or twinking as well. Any looser restriction would drive me to prove it over again with a tighter constraint, so this cuts past that slippery slope right to that endpoint.
And I'll cover some of the rules specifically in more detail. No mods is a hard-line starting point, which I'm absolutely sticking with. Once you start modding anything at all, it's a slippery slope to tweak and customize everything you want until the game barely resembles the original at all. I take this hard line with all the other writings you see on this site as well, the Civ series and FTL and the others. Any mod is not the original game; only a fully unmodified game truly represents the standard of playing the original game as it is rather than some individual wishing of what it might be.
I'm also fine to go without the common particulars of would-be mods. This includes no uber bosses offline, which I'm entirely okay with, keep the focus on the real endpoint of Guardianship. And this means no ladder runewords, which is a play style I also very much prefer. Because this forces you away from handing every single character and merc a one-right-choice Spirit or Insight runeword, but rather makes room for more varied options.
No additional stash space or mule characters. (I'm using the ATMA program to transfer items, but only directly between the characters, no extra stash file.) The stash is the size it is for good reason. Back during the game's heyday and active patching, Blizzard consistently rebuffed requests for more stash space, with the directive that the game isn't meant for accumulating infinite treasure forever, but you are meant to make choices about what your characters will continue to carry. And I want my game to operate that way. I want to be forced to get rid of marginal stuff, or else I'll end up with hundreds of choices for every equipment slot and take weeks to sort through them constantly.
No respecs. This is my rationale: respecs erode and eliminate the distinctions between builds. There is no such thing as reaching Guardian with different builds of the same class like a hammerdin or zealot or vengeadin, since any character could just do it with that class's most powerful build and then respec afterwards. I want to preserve the diversity and distinction of different ways to build characters. This includes having to get by the early acts on limited and makeshift skills and equipment -- figuring out all of that can actually quite be one of the more interesting areas of the game, that gets lost under most modern play styles.
No farming/repeating/rerunning areas or bosses. This is also to avoid a slippery slope. Without this rule, the right thing to do would be to farm endlessly in easy areas until all the equipment is as perfect as possible before moving on. I'd spend weeks at each such breakpoint like Mephisto on each difficulty or the Countess. I need to be moving onwards continuously. This is also the right motivation to clear areas and play through the game properly, to extract the maximum benefit from a single pass, rather than slip into the temptation of skipping and teleporting past anything inconvenient. Seven characters worth of full-clearing is just about the right amount in total; each character has access to items approximately as if they had recleared areas seven times themselves, which is just about on the borderline of how far you might reasonably go for that.
And finally, character death. That's an issue for any hardcore project, of course. I play hardcore because that's the only way that winning means something. There is no victory in softcore because there is no way to lose it. But a Hardcore Guardian is always an accomplishment. Sadly, however, a character death would upset the symmetry of a team project. The obvious answer is to rebuild a new character of the same class if someone dies... but I'm not thrilled with that option, that's actually a secret motivation to get someone killed, as a hidden way to respec and to run the replacement through an extra series of acts for more equipment. Upon starting this project, I haven't made a final decision of how to handle character death; I'll see if or when it happens and under what circumstances, and make the decisions then.
One thing that is allowed: save and exit to get out of a dangerous situation. I've always considered that legit. The realms have always allowed that and I don't want to take that off the table. Any restriction against that is difficult to enforce; I could just pause the game and wait until a power failure or something shuts it down anyway; and there's no record in the character save file to verify if you ever did this or not (as there is with the respec quest.) Reacting in time to hit escape to pause is fully part of the gameplay. So this is fully allowable and I'll use it when necessary.
And what I found by playing it, was that I absolutely loved this format! This structure hits a perfect sweet spot of making item acquisition interesting. You're still a long way away from the known elite power-optimized gear packages, but seven characters do indeed turn up quite a bit more equipment than a single one playing solo self-found. With this format, every mid-level exceptional unique is exciting, every mid-level runeword like Lionheart is scarce and thrilling when you can assemble it... but among seven characters, you probably will get the components for what you really need, and almost every one can find a useful place among an array of seven recipients. It's almost like playing 49 games at the same time, since items found by any of the seven can go to use by any of the seven. The possibilities explode wonderfully and I love it.
And this avoids twinking. The idea is that every item is sourced from somewhere that a solo character could have gotten it themselves. Every item only ever gets used forward in time from where it was found; nothing can come from a later act or difficulty and be passed backwards in time to be used for an earlier one. And every item travels through the game once and only once; we don't get cases of an item like a single Gheed's Fortune or Stone of Jordan getting passed around to be used by everybody to traverse the same acts many times. This is the closest I can get to a multiplayer team party environment playing by myself.