Studded, bone, and stone have the same LMC bonus, as long as "Mage armor" is stripped. The midnight bracers (obviously a necro item) and cuffs of the arch mage are both bone, which can have "Mage armor" stripped.
Gargoyle Stone has a slight advantage over studded and bone when enhancing for luck, as the resists get more evenly spread.
A bone and studded skirt (new item type) would be nice to add, but that's probably more work than just adding a bone or studded version of the legs. Likewise, some sort of bone gorget would be interesting, obviously an entirely new item.
"real" necromancers are probably in a form, like wraith form, where LMC is more interesting to play with. One problem with LMC is "rounding errors" in the mana calculation. Mana cost is round up if not a whole number. I'll post something more detailed on this at a later date.
You're right that studded or bone would be good, though bone would be more on point with the event.
The vortha medallion is a bit of a wrench in the works for a necromancer, again due to LMC and rounding errors.
An Elf (or gargoyle) using the spell woven britches leg item can be better off with SDI 10 over the new greaves, depending on the rest of the suit.
