Wouldn't it just be easier to implement an item that caps your ability to progress, if you're truly interested in grinding the lower level tiers? Buy the item off a vendor for free, if the game sees it in your inventory or on your person, you can only flag through X tier. You could also limit the ability to receive overpowering MGB buffs you don't have access to and basically make it as grindy as you want. I guess I just don't get why you can't experience a more classic feel on the server as it is, since all the content exists and the only limiting factor is your willingness to restrain yourself from continuing to advance through higher tiers if all you're after is the nostalgic feeling of lower tier content.
I think what drives a server the most, other than awesome content, is community and playing along with other people. In my experience, at the point where the server is now, you're pretty much doing your own thing in the high end tiers, and the lower ended tiers are basically empty. If the lower ended tiers was all there was, it would be much easier for new people to get into it, and there would be more people around where they are when they start up.
Its not 'just' about the grind, but its also about the grind =D Also, I realize that this is a "piss your pants to keep warm" solution to the problem, but I think for atleast a year or two, it'd be great.