I can get behind this.
I think resonance could be useful but its current incarnation has negative gameplay value. Either you are not hitting it at all in any meaningful way and it winds up just being one more book keeping task when using consumables or you are an alchemist and you have to fight and game your way around it as best you can and its all hindrance with no real feeling of benefit.
The fact that items still have per day usages and charges to track after adding resonance baffled me. It would have been simplier to do the more limited things per day having higher resonance cost. Overall it is a system that just needs to be sat down and think what they actually want it to do.
I think I had a simpler approach to the Resonance issue as it pertains to potions. Everyone gets one free potion/elixir a day. Any more, and then you run into Resonance costs. Now this can both help and hurt the Alchemist at various stages. The freebie could very well be an Elixir that the Alchemist has already infused. But this makes it possible for a character with no Resonance to still have a potion/elixir they can take for an emergency.
As for the wand issue, I think that we should change the wand's charges from a countdown to a count up. Give wands a Resonance limit as to how much it can handle before it burns out. Wands tend to be a more disposable item in comparison to staves. If you want a wand to be more useful over a longer period, then perhaps have the wand cool down one Resonance per day unless the limit was reached. But at that point, we need to consider the possibility of a smaller use limit on wands. Maybe 5 limit at most.
I like how Resonance works with magical staves. I never liked the whole "I need to cast the spell into the staff for it to gain charges" thing that PF1 has. So staves are currently where Resonance has the carrot going for it. It feels more like the spellcaster is using what dregs of magic surrounding them to power the staff. And casting with the staff is as simple as forming a magical link between the caster's intent and the staff's reserve of magic. It feels right.
I do feel that scrolls need to be opened up to more than a caster only kind of item. There's something cinematic about the party rogue or fighter breaking out a scroll in an attempt to save the party from a terrible threat. Other than the "needs to know this spell to cast from this scroll" thing, I think Resonance works perfectly fine with scrolls. Again, I picture it as someone trying to summon up the magical energy to power the scroll.
Investing into other magical items is a hit-or-miss situation based on what they are. Investiture plus activation costs are probably the most irritating part right now. We could apply a text that indicates that the initial investiture gave the item a free use of its activated ability.