Another option that not many people initially think about:
Fastcast and M.Acc
Makes a great Aspir, Drain, Stun (for blm, sch and rdm), for enfeebling songs (for brd)
Adding M.Acc and MAB will be one of the best nuking pieces for SCH and RDM (after morrigans). It will be interesting to see how it compares to Weskit for BLM
I think the Macc and MaB options should be slightly higher... but it does open up some fun macro swaps. But it's mostly a SCH's piece, since they are barred from significant nuking gear elsewhere.
I think the fast cast is the most significant mod available for this since, aside RDM, you'd need marduk body to get that, and not all the jobs on this list can even use marduk. It's not comparable to morrgian's, and for BLM it looks to be on par with HQ weskit.
I'd suggest Fast Cast and MaB. If you're worried about resists use AF1 for SCH. SCH/rdm with this, AF2 head, and AF1 feet will be able to idle in 50% fast cast.
What I think will happen, is that people will make "free" replica's or alternatives of other expensive gear. This will lower the demand for, say an HQ Weskit because many main BLMs may switch/choose this body instead. Its popularity may also lower the price on Ixion Cloak etc. So more people will have easier access to good nuking gear one way or the other.