I'm not sure all the heros should have one, but I do like the idea of giving it to a lot of them.
I don't think any of the civs with multiple heroes/world units (Doviello, Lanun, and now Kuriotates) should get equipment. It could be nice to make Lucien start with Iron weapons though, as he does seem to be the last Doveillo with a finely crafted metal weapon.
In the case of Sphenor, I'd say that he should start out carrying the Sword and Shield from the Symbol of Junil at the Seven pines. I think making this provide Law affinity could be cool, or maybe a bonus vs. demons/undead/HN units.
While I'm not sure I like the name "Loki Gem," an equipment that lets other units use taunt could be quite nice.
I'd like to give Basium a war hammer that prevents units it kills from returning as manes (unfortunately the code creating manes only checks for the civ that killed the unit, not the unit) and has some other bonus for defeating demons too, like giving units in the stack warcry when it is used to kill a demon.
I like changing the Gela to provide Entropy affinity instead of just +2 unholy strength, and make it allow those wielding it to cast a spell similar to Domination that works on Demons, probably requiring AV stats religion.
I think that the Mithril Golem should drop a new Pieces of the Mithril Golem equipment when t is destroyed, which just like the Pieces of Barnaxus would let it be rebuilt.