I don't like strangling Mir to limited choices of bosses either.
There's been calls for having other versions of WT (to keep banging on about WT, but it's an easy example everyone is familiar with), stopping higher levels going there cos they have another WT to go to.... I don't like this either. I think all players should be able to go anywhere. But if you're too low and go to a high cave, you'll die - lesson learnt. If you're too high and gain nothing, you'll get bored - lesson learnt, and hopefully the pizz taken out of you if you're way too high for it.
No pk'ing goes against the game, imo. Outside of a war situation, I would however severely punish players for killing a player much lower than them on a frequent basis, to be defined. You can't stop players killing lower levels completely, as as described, you can get lots of greifing off the back of it. Standing on drops, blocking entrances, blah blah..
Going back to the call for 'other versions of WT' - this is very lazy imo. The game, atleast the last time I looked at my server files, has so many mobs and dungeons, you shouldn't have to do this.
Best way to resolve this, is for hosters to have a number of "trusted people" play the live game from level 0, and feedback the issues they had - to BH if you like, in this case, of the likes of BH themselves. List the issues, and do something about it. But don't knee-jerk to the extent of wild changes that screw things up across the board. Players with no time to be 'serious' levelers would be ideal for testing the game for new players.
A response of 'you can get to 40+ fairly quickly' makes me cringe. I would expect, by now, that all those who'd want to be level 40 quick - are - and those who get dragged into playing the game again will have mates who dragged them in, so they can help them. Apart from this, you have the 'new' players who haven't played for ages, or never before, and go from server to server, probably until they get ganked regularly, then quit and move on. You need to keep these people. Besides, the game does have a mass of content up to level 40, WT for example

, shimmying people up to 40, you may aswell have a level 40 starting level and skip all the other content. As much as these hardcore players are valued, doing what they'd like the game to be will slash your user count until only them are remaining. It's happened again and again in Mir.
Ignore the content that the 'serious' players care less about and you'll have a server of dozens of these players, hell bent on 'yo mama' each other, and b1tching alot, instead of lots of pockets of different levels doing their own thing that amount to hundreds. Worse than that, the dozens of player will know all the spawn places, all the times, and will eventually camp - or as good as. Or server hop, where you log into a server when you know something is about to spawn.
That there's not enough "small time" bosses for every single user in the game.
Basically it's no good limiting people to level caves as it stands now because then people will actually start wondering wtf is there to even do inbetween the SIX HOUR respawn times of the huge bosses.
More content = Problem solved. Make a higher level version of WT with better drops THEN level cap the lower level WT cave. Problem solved. Same can be said for any noob cave that's worth hunting (EC, GK, WT) If there's a higher-level (40+ version) of it that's soloable/duoable then it'll keep those people happy and at the same time allow noobs to have their GK, WT, EC and their entire cave to themselves.
Koriban knows the score, I'd go about it differently tho.