Here are some things I think could improve the Alchemist as well as things that pertain to it. These aren't in any specific order, I just wrote them down as I looked at the class again to give my thoughts.
If I'm mistaken about anything or overlooking anything please let me know. If anyone has anything to add please feel free.
1. Low level Alchemists are very bad. If you do anything except max your intelligence and dexterity and take Quick Bomber you're basically going to be the weakest character in the group and even then your options are VERY limited. Assuming the Lost Star adventure is a normal indication of how many fights a party would get into that means it could be anywhere from 4 to 7 encounters in one adventure. That means the alchemist would need to have 8 to 14 bombs at first level in order to be able to use 2 of them in each of those encounters. You might say "well casters don't have that many 1st lvl spells" while that is true casters also have at will cantrips which some are pretty much guaranteed to cause damage, even if it's only half a d6. Alchemists on the other hand will only have anywhere from 4 to 5 resonance (barring being a human and getting Remarkable Resonance at 1st lvl). That means if you only make bombs, which kind of defeats the purpose of having other alchemical items, you can have 8 to 10 but that means no healing, no tangle foot bags and no cheetahs elixir. So the more you want of these items the less useful you are in combat. Which I can understand if they wanted the bombs to be similar to the casters spells but again Alchemists don't get cantrips. So once they run out of bombs they become useless.
I suggest adding either more resonance to use on bombs, allow full batches with Advanced Alchemy or something that gives them a type of cantrip ability, like this;
Junk Bomb
Every time you make a batch of bombs during your Daily Preparations you have enough salvageable materials to make 2 Junk Bombs. Junk Bombs do 1d4 damage and have 1 splash (the damage caused by the junk bomb is the same as the base bomb, so in making a Batch of Alchemist's Fire you would end up with two Junk Bombs that do 1d4 fire damage and 1 splash fire damage). Their damages scales with your Empower Bombs ability.
Something along those lines would give the alchemist a sort of cantrip type ability that would really help their longevity as a class.
2. The Alchemist has no melee option whatsoever (other than poison) until they get mutagins at lvl 5. It would be cool to have something that maybe makes your sword flaming or acidic for 2 rounds. That way if an Alchemist wanted to melee there would be the option other than going all Mr. Hyde (which is awesome but still)
3. The fact that a poison is wasted on a miss is pretty harsh. You have to take 1 whole round applying it (unless applying it before combat) and then one bad roll and it's just gone? I think it should just be wasted on a crit failure. It would make them much more appealing I think.
4. All 1st level feats except Quick Bomber aren't that great. Alchemical Familiar has no rules for its use with an Alchemist and can't actually help you, it's basically flavorful. Alchemical Savant is nice but compared to being able to draw 2 bombs in one action it's hardly worth getting. Far Lobber only increases the distance by 10 feet which is not comparable to being able to throw 2 bombs in 1 round. Smoke Bomb is.... I don't want to say useless but it basically is, especially at low levels where you would again feel the need to throw more bombs because all of your other options are terrible, bad ranged and bad melee. I understand that you get to have 2 of these because of the 1st and 2nd lvl class feats but again some more variety would be nice.
5. Quick Alchemy in its current form needs work. I've been making an Alchemist from lvl 1 to lvl 10 and putting them against random monsters to see how they do combat wise. It was ALWAYS better to get 2 bombs/elixirs from your daily prep instead of having the flexibility of Quick Alchemy. With the current state of things you would possibly only save 1 resonance for Quick Alchemy and then just try your luck on overspending. It is a lot more useful by the time your level 9 but it's kind of late for that ability.
6. Making the Elixirs still cost Resonance points to use for other party members (after you've already spent RP to create them) doesn't make sense. This makes the Alchemists not even able to be the parties discount Cleric which would have been really nice. Having two different classes that could give Resonance Free Healing would have made the Alchemist more appealing I think.
* Also making Alchemical Items not cost Resonance at all could possibly be an idea. Elixirs of Life aren't as good as Potions of Healing, and they are generally higher lvl, so they won't be as accessible but still a viable option for a non caster party as a means to heal themselves. Some tweaking and maybe adding in a way to get Alchemical Crafting at lvl 1 would be a must. Maybe creating a background that gives it to you? I think this is a smart option as a non caster party is going to be a death wish.
7. Remarkable Resonance should go off your Resonance ability score and not just Cha. Dwarf Alchemists will have a really hard time getting that feat and it's basically a no brainer for Alchemists.
8. Two of the four Alchemists feats at lvl 4 are, again, not great. Being able to make 8 regular items in a batch during your downtime or being able have your Int modifier to your splash damage are WAAAY better options then poison resistance or having your Quick Alchemy item last for 1 more turn. More options please.
9. Combine Elixirs is cool but the RP cost is too heavy. Finding a way to make it not cost so much but still do relatively the same thing would be ideal.
10. Tricky Tinkerer does not seem like an 8th lvl ability, a 4th lvl one more like.
11. Having the Alchemical Items listed by type and then alphabetically in each one would be very helpful.
12. Being the only class Trained in Alchemical Bombs their proficiency with them never goes up. They only get an item bonus at 15th level when using empowered bombs, which also seems really late. I get that they throw against TAC but even spellcasters proficiency goes up. It just seems strange to omit.
All in all the Alchemist just seems to need some low level balancing as they seem to even out at higher lvls. Not needing to spend money (and RP) on magic weapons helps with the RP overload but they still seem to be pretty stretched even at higher levels