isn't that basically what LoN already does? you just need ancient versions of it. I doubt it'd fix anything though, most "non-meta" legendaries have multipliers that are way too low compared to the high tier or percentage numbers for effects that barely tickle anything
LoN buffs all ancient legendaries. On top of that, the new amulet would give an extra buff for all those miserable legendaries that devs would grant with a lowered tier.
So you could use the new amulet with LoN and get over 2000% increased damage with poor legendaries making it sub-par with a some set bonuses. Of course, you could mix a few good legendaries in as there's LoN for a legendary bonus + only the LoN bonus.
Quick LoN + new amulet example as I'm in hurry:
Helm: Tempo of Twilight (low) +200% (100% from LoN and 100% from new amulet)