What would be the effects of allowing dual Pact Weapons?

I have been considering a Hexblade Warlock with a houserule to allow two Pact Weapons, so that they could dual-wield. What would the effects of such a houserule be? It is an extra option for Pact of the Blade, but is it stronger than things they can already do? It doesn’t seem like it to me, except maybe with the Improved Pact Weapon invocation giving two +1 weapons. But even that doesn’t seem too bad considering Polearm Master could basically do the same thing.