I'm not going to dredge over every point already made, you can go read Locomonkey's original post, and Taepsilum's well reasoned list of what the pitfalls to avoid in such a system would be. Instead, I'm going to speculate on how you could address those pitfalls. How do you make a system with so many potential raids tuned and balanced, deal with all the updated loot from those instances, and keep from drowning raid groups in choices? My suggestions are as follows:
Back at the end of Cataclysm, Blizzard introduced a series of Summer Challenges, the purpose of which was to challenge the players to go back to older content. In my opinion, this kind of activity would be a perfect way to make use of an updated older raid. Imagine if Blizzard updated the current level 60 raids (MC, BWL, and the two AQ's) to level 90 10- and 25-man raids, and then opened each raid in turn over the course of a month. So for April, you'd have Molten Core Challenge Month, with an updated MC available for your raid group to go explore. Then in May, Blackwing Lair would get the same treatment, followed by Ruins of Ahn'Qiraj, and then Temple of Ahn'Qiraj. By rotating the updated raids in and out of circulation, you prevent guilds from feeling that they have to try and run 16 raids in one week, and by leaving the raid accessible for a month you give groups time to schedule a run or two inside the updated raid.
This could continue, month by month, until we'd gotten through the BC, Wrath and finally Cataclysm raids. It's likely that this kind of process wouldn't be completed before the next expansion started -- which is fine, because it just means you'd plan out which raids to update to 90, and which ones to hold back to update to 95 or whatever max level in the next expansion will be.
2 - Don't make the gear cutting edge
There's no reason the gear in these updated instances has to be as good as the current raid, either. To make an example, let us suppose they had the four original raids ready to roll out under this system right now. Why itemize them as equal to Throne of Thunder? If they were merely as good as MSV or even HoF/ToES, they'd be compelling enough for people to go get gear for alts, offspecs, or just for guilds that are behind the gearing curve and would like another option a week to gear up for newer content.
For that matter, see number four on this list.
3 - Don't worry about heroic modes or making the mechanics as challenging as modern raids
As long as the numbers line up, just let Garr and Geddon work as best you can with the current raid numbers. Leave perfect tuning and balancing to the current tier of raiding, and let these nostalgic older raids be updated so that modern groups can go in, get a sense of what they were like, and move on. I mean, not many raids are going to have the number of tanks and warlocks necessary to banish or offtank all of Garr's adds, so don't worry about keeping that mechanic alive. Close is good enough for this kind of content, and leaving it undertuned is fine, since it'll only be around for a month or so before it's replaced with the next one in the calendar. Think of them as bigger, flashier, nicer versions of holiday bosses.
4 - Do include them in LFR
In fact, you might even want this to be LFR only. That way, you don't need a 10- and 25-man version of it. You'd just scale everything up to 25-man, and you'd only have to worry about tuning the mechanics to that grouping. Similarly, making them LFR special events means you could even keep them around after the month is over by making them a Random LFR feature, letting people run a random old raid as a bonus shot at LFR gear for the week.
In fact, making this a part and parcel of LFR from the get go solves a lot of problems. It allows people to run this content without having to convince a bunch of other people to run it with them, it means that once you had a sizable chunk of older raids converted you could keep them going by cycling them through a random LFR feature, and it makes transmog runs easier because you could run the raid with your friends on normal, and then go to LFR if you didn't get your drop this week (like, say, when I killed Gluth and the Four Horsemen this week and my sword didn't drop arrrgh.)
These are just some ideas for how this kind of system could work, and by far they're not the only ones, nor do I claim they're the best ones. How about you? Do you have ideas on how to keep such a system from becoming overly cumbersome and a drain on current endgame resources? I do like the idea, but I also think it would definitely need to be watched to keep from becoming a quagmire. Nice job, Locomonkey.
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