I'm kinda sitting here wondering what other artisan's tools you could make subclasses out of, since it seems like the subclasses for the Artificers are based primarily on the tools you use (alchemist's supplies and herbalism kit for Alchemist, and Smith's and Woodcarvers tools for Artilierist)
Assuming there's no crossover of tools, you could make something with Jeweler's Kits and Mason's Tools and be a kind of elementalist (like real life Periodic Table elements, not The 4 Elements type thing). Part of your crafting specialty could be those spell gem things that were in OotA (basically spell scrolls, but you can't write them into your book)
There's also Calligraphy Set and Artist's Supplies for the artsy types who paint pretty pictures of what they want to happen and it happens. They would probably focus on Spell Scrolls for crafting.
Heck, if they don't care too much about different subclasses getting the same proficiency, they could use Herbalist's Kit and Woodcarver's Tools to make an Apothocary subclass that would focus more on healing, and let Alchemists throw greek fire and poison gas around.
Really, the more I look at the tools, the more ideas I get.
Kinda think they should get another skill proficiency, but I understand that they don't, considering all the stuff they put into Xanathar's about other uses for your tool proficiencies.