Potential lockout-solution

To the players that would participate with a lockout to play with their friends / play with others.

Have a (practice) arena.
Rules:
You can start from any save point up to the point that the furthest progression member has unlocked in either practice or BCoB (this week). Practice does not count for BCoB progression.
There is NO loot / gil in practice
There is NO armor damage in practice
All turns are the exact same as they appear in BCoB (no reduced damage or other changes)
There is NO lockout for practice mode.
Practice mode has twice the event-time as normal BCoB runs (in the expectation that you would not finish in a regular run you are allowed more time to practice)
Practice mode will be available for dungeon search if not server-only duty finder.

This would allow players to go back and 'help' their friends learn the mechanics of all the fights, it would NOT increase the availability of any equipment. It would not cause a gil drain either.

How about allowing a second lockout for a second class? Yes sure, you get a chance at double the loot for a single class, but to be honest, I don't see the harm in allowing people to do this. If players want to blast through gearing for a class to get through the content, then let them. Let people play at their own pace.

I know that some people will use it to "carry" others through and so be it, if that is the choice that a player makes and has enjoyment in that, let them! I can easily see the majority of the player base taking that second class to run through with other FC members that may not be as lucky to get into static groups due to scheduling conflicts or fill in when someone can't make it for a night or dare I say, just to have fun with people they deem as FRIENDS.... It may sound stupid, but a lot of gamers often see other guild/fc members as friends and isn't this what a game is all about? I personally run coil early in the week and then have the oh so much enjoyment of watching my FC chat cause a group is looking for another all because of someones real life.

Real life should always come before a game, but what about the other 7 players, their night could essentially be turned to a waste because of 1? Even if I have 7 other Jobs at 50, I'm not allowed to run with them cause I ran it on one of 8 available Jobs?

Guess what? If random group A wants to run through twice in a week and funnel gear to their main classes in order to clear it easier the next week, that has no effect on my or others enjoyment of the game. Even more so, those people are more likely to enjoy things even more running through a couple times a week getting all their jobs maxed out were as I am just having a good time playing with 1 or 2 jobs.

I can see the Dev's point with basically having the road block for access to gear. As those end game raiders who have completed turn 5 point out, after you've done that ... what else is there? This would help allow those not at that level to prepare for it, or those who have problems playing with others the ability to get in to the content with people other than their static if only for the option to play.

Perhaps this has been discussed before, but I still don't understand why a gear lockout wouldn't solve the issue. It would allow people to go through and help their FC members through turns but they'd only have the chance to roll on loot once per week (just like it is now). In theory this is no different than those FC members running with PUGs because they weren't able to do it with their own FC, so it's not really like people are able to gear faster than they would have been able to. Additionally, it would help people get more practice at turns in the same manner that the OP described.

Surely it can't be that hard to implement a system like this, right?

I like the motivation behind this, but I don't think this is a particularly interesting solution. It's a manner of perception...If you call a fatigue system a fatigue system, then naturally players will look at it with derision. If you call it bonus xp, they'll love the hell out of it.

Similarly, you have proposed a mode where players can primarily enjoy the content and learn the mechanics without dealing with lockout. In return, no loot. The problem is, I think, calling it "practice mode." If developers announce "practice mode," then it doesn't really feel like a new content mode.

On the other hand, if developers add a "time trial" mode, with no lockout and no reward other than a weekly world announcement to the team that beats the dungeon most rapidly, it feels more interesting, no? "Hey, anyone for T2 time trial mode?" vs. "Hey, anyone for T2 practice mode?"

As far as armor fees go, in the end game it really isn't that expensive(remember that tomestone mats are still going for 15k/each).

People complaining about lock out because those not in a static group cannot get any gear, so implementing a no loot system will not help at all.
If someone really want to practice (so they can join an experienced PUG), they can just ask their friend to go in with them and deliberately fail at the very end.