@Cylux
That may be so, but I can hope to have it added for Zealot. 
It’s worth noting that Grail Knight is equivalent to a career path in the skill tree in Darktide since they changed their approach to subclasses in this game. They have done several skill tree reworks in the past, including with the coming update for this Tuesday, so I don’t think it’s unreasonable to expect that this feature could be added to Zealot.
Would be nice.
Since both Arbites and Hive Scum have mid-tree keystones that can be combined with the bottom-tree keystones, that might be a good way to implement dual-melee for Zealot as well. Instead of attaching the node to Blades of Faith, dual-melee could be a mid-tree keystone. In that case it could have the 50% weapon swap speed and maybe other minor buff, excluding the throwing knife bonuses.
This could also be a good way to give Zealot some ranged damage benefits. There could be a ranged-oriented keystone that’s mutually exclusive with the dual-melee keystone. The ranged keystone could give a bonus to ranged damage equal to X% of your melee damage bonuses, or some kind of ranged bonus for several seconds after a melee kill or melee crit. This would add build options both for players that want to go all-in on melee as well as those who want a more balanced playstyle on Zealot.