I'd like to know if someone came up with ideas (feats, rules, etc) to craft wands and potions that replicate spells above 4th-level and 3rd-level respectively.

Thanks for the help ^^

Off the top of my head I might (and I stress might) consider greater Craft Wand/potion feats.

Craft greater wand - allows crafting wands with spells up to level 7

Craft grand wand - up to level 9 (VERY Leery of this, but since staves can accomplish something similar i think it would be fine.)

Craft Greater potion - up to level 6
Craft Grand Potion - up to level 9

All costs scale, etc

You could make a wondrous item in the shape of a stick that can cast spell X 50 times.

You could make a wondrous item in the shape of a stick that can cast spell X 50 times.

Or just take craft staff or Craft Rod. The both potentially being infinite times per day

I think Forgotten Realms (3.0) had a prestige class (master alchemist?) that allowed you to make potions higher than 3rd. It was in Magic of Faerun IIRC.

Dreaming Psion is correct.

Really the thing with wands is that there isn't really much need for what they do at a higher level due to Wondrous Items and Staves, and it can be... problematic for random treasure generation. Especially if you have such things as a wand of miracles or a wand of wishes. Granted, GMs can and should choose to negate such things, but... many don't. I suspect that's one of the reasons such things are limited in that way.

My recommendation is not allowing them to be generated as random treasure. Looking up Magic Item Prices, such items would be difficult to come by in creation, but it's still possible. Basically anything that costs a lot is recommended against as a randomly generated item.

Still, I've definitely thought about it (and even indulged a time or two in past games I've run).

As far as potions go, well, I honestly don't see the deal. Again, it's a way to limit randomly generated treasure, but, personally... meh. There are a lot of effects that can be made into potions or oils, and that's really neat and all, but I'm not seeing the point in limiting them to only three levels of spells. Still, adding additional feats or creating a prestige class (or simply porting it) that allows higher levels seems totally fine.

A quick Export-lite-version (feel free to tweak, ignore the formatting, I'm in a bit of a hurry):

Master Alchemist
Requirements: Skills [Craft (alchemy) 7 ranks, Spellcraft 7 ranks], Feats [Brew Potion, Skill Focus (Craft (alchemy))], Spellcasting [4th level arcane or divine spells]
Traits: d6 HD, 2+INT skills, good will saves; worst BAB, worst fortitude and reflex saves
Class Skills: Craft, Knowledge (arcana), Knowledge (nature), Knowledge (religion), Profession, Spellcraft
Spellcasting: At each level you gain +1 level of existing class as normal for a full spellcasting PrC
Benefits By Level:

• 1st: Brew Two Per Day
  
• 2nd: Brew Potion (4th Level)
  
• 3rd: Brew Potion (5th Level)
  
• 4th: Brew Potion (6th Level)
  
• 5th: Brew Three Per Day
  
• 6th: Improved Identify Potion (can use Identify on potions at will, by taking 1 minute, at no cost; this is not noted as being an extraordinary ability, spell-like ability, or supernatural ability in the original book)
  
• 7th: Brew Potion (7th Level)
  
• 8th: Brew Potion (8th Level)
  
• 9th: Brew Four Per Day
  
• 10th: Brew Potion (9th Level)

That's more-or-less exactly what is printed in the book, though the skill ranks are modified to be the equivalent in PF, and the formatting is, obviously, atrocious. I might shift the Brew x/day around a little bit, put Improved Identify as a 5th-level ability, myself, if you would choose to use this.

Originally the class required a feat called Magical Artisan (Potions); the magical artisan feat reduced the cost to create an item (in gold, time, and XP) to 75% of the base cost. That feat doesn't exist in Pathfinder, which is why it's not listed above. As a partial offset, I might recommend making the class require Profession (herbalist) 7 ranks and/or even Skill Focus in that skill. I changed the description and name of the Improved Identify ability to Improved Identify Potion and what you see written above you, because the text spelled out that the Master Alchemist could do exactly what the Identify spell does in Pathfinder. I figured it would be easier just to link to that and be done with it. I might recommend making that an extraordinary ability, though. Brewing additional potions per day should probably remain a typeless ability (that is not extraordinary, supernatural, or spell-like). Also, I changed the 3.0 Alchemy skill to the 3.5 and Pathfinder Craft (Alchemy) skill, which is the same thing, just with slightly more streamlined mechanics.

If you preferred a feat chain, while I like TCG's two-feat idea, here's an alternate (although it's not balanced with the above at all) that I might recommend (mostly for math-style symmetry):

• Brew Potion (as written) four spell levels 0th-3rd
  
• Improved Brew Potion (up to 6th level spells) three spell levels 4th-6th
  
• Greater Brew Potion (up to 8th level spells) two spell levels 7th-8th
  
• Master of Brewing (up to 9th level spells)one spell level 9th

Feel free to change the names if you use that idea.