I'm probably thinking of "creating and animating a tiny construct over the course of a long rest" rather than "casting the spell on a random object." But the net effect would be the same.
You could start at a lower level with a Find Familiar, then improve to the animated object spell from XGTE. (Can't remember the name of the spell.) Possibly then on to creating Homunculi at higher levels.)
First of all, thank you for your very constructive input in this thread.
The spell you are thinking of is tiny servant. I think I would start it at level 6, and "modify it" thus:
- Tiny servant is animated for 1 hour/level (normal spell is 8 hours)
- Tiny servant can communicate simple concepts via gestures (improves utility)
- Tiny servant's HP = int bonus + alchemist level. This makes the starting HP roughly equal to the spell but it scales up, without being a ridiculous meat shield
- Tiny servant can be repaired by the alchemist during a short rest, gaining 1d10 HP.
- Tiny servant can use the caster's infusion (I haven't really thought out if this could backfire somehow)
One alternative that I've considered is making artificers full casters, but requiring their class-based magic items and construct companions to be powered by spell slots. So at 2nd level for example, the Artificer can spend a spell slot to empower a couple of small objects as Sending Stones at the end of a long rest.
This fits well with using the construct-animation spells with XGtE quite well actually.
Full caster is a lot of work...
If you allow magic item creation in your game, then Artificer is definitely one of the classes that would be able to make them.
They already can via wondrous invention - they make fairly low powered items like bag of holding, caps of swimming etc. But the common items in Xanathar's book are of even lesser power. It would be a nice ribbon ability, but it may be a bit too much on top of the existing wondrous inventions.