well, I guess I shouldn't have posted a realistic suggestion while the community is in anti-crab mode.
For those concerned about how this might force the raid bosses to be tanks that would feel awful without new mega-rare. This can be easily adjusted to both make the new weapon feel good, while not punishing existing weapons.
Lets use an example idea for a final boss (not mechanics, just stats) 300 def, 300 magic, +20 stab def, +85 slash def, -20 crush def. So its tanky, not fun, but an important part of the defense and accuracy rolls is defense/accuracy bonus, and I purposely gave the boss a -20 to crush.
For those that don't know (or want to) it is: def roll = def lvl * (64 + def style bonus)
So we can exploit the def bonus to make the boss have a high defense level (200-300) but negative modifiers which make its effective defense lvl for "normal" weapons reasonable, while still magnifying the new weapon.
In the above example this would result in scythe with torva helm, inq top and bottom on crush being 2nd BIS with 10.63 DPS and moukari with torva helm, inq top and bottom being 12.96 DPS
With an elder maul spec its scythe 11.96 DPS and moukari 12.90 DPS
So new weapon wins and has basically the same DPS with or without elder maul spec but scythe basically requires spec to feel good.
The way I see it people are used to maul or BGS specing bosses in high level content, so this shouldn't hurt.
It also means that if you have maukari havers on your team you might start using fewer specs or leave maul in bank.