My UA character that will now be Light Weapons is going to be tracking down Light Axes or other full-power-swing light weapons. My sword character would be tracking down Heavy UAs.
Other characters will be seeking out armor pieces with the five new cantrips (Shield, Dirty Fighting, Dual Wield, Recklessness, Sneak Attack) on them. Bowyers will likely want XBows for some purposes, and vice versa.
And that's even before you get into the possible +25% to attack mods! People will want to hunt for those, too.
Before the weapon-nerf-as-far-as-PvP-is-concerned, I already had my work cut out for me in terms of new loot hunting with this patch.
I understand that sometimes loot needs to change to keep the playerbase engaged, but there's a time and a place for that, and that's when you introduce a new loot tier.
But you're not introducing a new loot tier. You're invalidating current PvP weapons without the promise of something truly bigger and better; we're basically just being forced to expend effort to tread water.
Imagine if, when you introduced GY gems or bunny feet, they only worked on new weapons that dropped!
Imagine how silly that would be!
That's more or less what you're proposing here, when you boil down to it.