| Level 20 NPC |
Step 1: be a half elf
Step 2: be a level 1 wizard selecting ther arcane builder discovery and gaining a valet familiar
Step 3: be a broodmaster summoner. As soon as you can, split you eidolon into one lesser eidolon with master craftman, wondrous items and cooperative crafting and one greater eidolon with the above AND sink the most evolution points possible on this guy to make up for the lost level (and the hit dice/feats dedicated to the lesser eidolon). The half elf favoured bonus will help.
Now, here's where things get stupid: you can basically play as your (greater) eidolon and let the summoner ONLY craft all the time when the party stops to rest. During the actual adventuring day he can rest using the keep watch spell (let him ride his eidolon so he can actually rest, kinda). During fights? Well, once your eidolon becomes large you could try to hide in its backpack i guess.
Honestly, you don't need many feats. So why don't you take the animal ally chain to have another damage dealer? Tha't great in case you feel like you're not actually contributing too much during fights. Then start with the mount/altered summon monster cheese combo and have some fun (my favourite option here are lillend azata and a banner of ancient kings to basically have a bard with you)
Now you can decide if you want your greater eidolon to become stronger, of it's okay for you to take some more lesser eidolons to keep speeding the item creation process even further.
For sure it isn't the best crafting build, but quite a fun one IMHO. Maybe let other players control some of your critters