How about adding a second Primal Focus Quest?

[Ultimatecalibur]

Well I'm not sure what the quest would reward, Shiva EX already gives a 100% guaranteed i110 weapon, which is more or less equivalent to the i90 weapon back then.

Not really. The Primal Focus Quest when introduced in 2.1 gave the equivalent of a Zenith Relics or a pre-buff Allagan weapon, the two endgame weapons. The equivalent reward right now would be getting an i120/i130 weapon and that in many ways is already covered by the Augmented Ironworks weapons.