I've been trying out PF2 with some solo adventures (that is, me GMing and controlling the whole party of PCs at the same time), and one of the things which has frustrated me is the very small number of spell slots. I don't know if it's just my playstyle, but I found myself playing my casters very conservatively, relying on the Champion's Lay on Hands and the Medicine skill for healing and avoiding using any daily resources if I could get away without them. In doing so, I discovered that unless my dice hated me or I found an enemy my builds were bad against, I could generally get through anything less than a severe encounter without spending any daily resources like spell slots. Thus I still had nearly all my spell slots when I reached the boss, and I was able to nova him and win easily and anticlimactically. For the rest of the battles, though, my casters felt rather unexciting - since I wasn't willing to cast their spells on fights where they weren't needed, they were stuck just using cantrips which rightly seem to be less effective than martial attacks. All in all, while it was an OK experience while I was playing the whole party, I think I would be rather disappointed to either play a caster, or play in a party with a caster if they were played in the way I was playing them. And yet that method is the one I gravitate to since I dislike expending resources I can't replace if I think I can safely avoid it. They're Too Awesome to Use, as TV tropes would put it.
(Digression: I think this effect is more pronounced than it is when I play PF1 because of the smaller number of spell slots making me want to hoard them more, and because the focus/medicine mechanics mean that hp isn't a resource you have to spend spells to restore any more, so unless there's an immediate time pressure I prefer to lose a few more hp and then rest for 10 minutes more rather than spend a daily ability to finish a fight faster.)
Rather than just complain about the issue, I've been trying to think of a solution, and I wonder about simply making spell slots recharge like focus points. Nearly everything else seems to recharge at that kind of rate anyway, including hp (if you have a healing focus power, or the right skill feats), so why not? Of course, you'd also have to decrease the number of spell slots you get, dramatically, to avoid overwhelming the noncasters and nova-ing every battle. I'm currently thinking of someting like this:
You get only 1 spell slot of each spell level you have access to. If you're a prepared caster, you prepare a spell in each slot at the start of the day as usual. If you cast spontaneously, then you can use the spell slot to cast any spell in your repertoire - use the official spell slot progression to determine how many spells you can have in your repertoire. A spell which lasts "until the next time you make your daily preparations" ends if you regain the spell slot using the Refocus activity. Otherwise, spellcasting works normally.
If instead your casting comes from archetype feats, you get one spell slot if you have basic spellcasting, a second slot if you have expert spellcasting, and a third if you have master spellcasting. These slots' levels are equal to the highest level slot their respective feats would normally give you at your level. For example, if you're level 14 and have Basic and Expert spellcasting, then your two spell slots will be 3rd and 5th level.
The Refocus activity is adjusted as follows:
Refocus (Concentrate, Activity)
Requirements: Either a) You have a focus pool, and you have spent at least 1 Focus Point since you last regained any Focus Points; or b) You are a spellcaster, and have at least one expended spell slot.
You spend 10 minutes performing deeds to restore your magical connection. If you have spent at least 1 focus point since you last regained focus points, you may restore 1 point to your focus pool. If you have any expended spell slots, you may restore any or all of them. If you are a prepared caster, the slots you restore are automatically filled with the same slot they had before you spent them. You must choose at least one of these options, but may do both as part of the same activity. If you are regaining focus, the deeds you need to perform are specified in the class or ability that gives you the power you are restoring; if you're regaining spell slots then you must do the same activities you do in preparing your spells at the start of the day. These deeds can usually overlap with other tasks that relate to the source of your focus spells. For instance, a cleric with focus spells from a good deity can usually Refocus while tending the wounds of their allies, and a wizard of the illusionist school might be able to Refocus while attempting to Identify Magic of the illusion school.
Obviously, this is not a finished house rule. I'm not really experienced enough in the game to predict all the knock-on effects or judge what effect it will have on balance, so I'm posting here to ask: is this viable in principle, or will it break the game for some reason? As written, are martials and casters reasonably balanced in how much they can contribute to an encounter, or would it be better to be more generous/stingy? Does it make spontaneous casters too strong compared with prepared ones? How about archetype spellcasters? Which special abilities will need rewriting which I haven't noticed? How could they be rewritten? Are there more obvious solutions to the "Too Awesome to Use" problem which I haven't noticed?
Alchemist: Will need some equivalent recharge mechanics for its own daily powers
Cleric:
Divine Font gives several max level healing spells per day. Could become 1 extra highest level spell slot for heal, although that loses the charisma dependency.
Wizard:
Arcane School: Doubling the number of spell slots is obviously too strong. I'm not really sure how to adjust it down while still connecting a significant proportion of your spells to your chosen school. Perhaps some sort of buff for any spells you cast from the appropriate school, or an extra archetype-style spell slot progression for spells of that school?
Bonded Item: Probably OK (casting a spell twice in one encounter 1/day) but a bit hard to balance against whatever adjustments are made to the arcane school.