Personally I think it's fine to invent a Creo spell or effect that creates a flawless tool. After all, you're pulling from the realm of forms.
I'd say +3 magnitudes gets you a flawless tool, and another +2 lets you do a group of different tools at once - so +5 magnitudes. Sun duration is probably acceptable, but you'd want unlimited uses. Requisites for additional materials I'd class as free requisites, so no extra magnitude but you still need to account for the art. That said, you could create a set of jewelers tools without requisites.
So at the end of the day you end up with:
CrTe 60 (base 5, +1 touch, +2 sun, +2 group, +1 size, +5 complexity) : once/day, so no night-time lab work!
Honestly, if someone is prepared to invest in a 12th magnitude effect to improve their lab, I think they've probably earned it. A level 60 effect isn't a casual project in any games except very high-power ones. You're looking at a lab total of 90 to do the project in 3 seasons (1 to open, 2 to invest), or a lab total of 120 to do it as a lesser enchanted device. Even with a magical focus this is not a junior-magus project. It's a significant project for a magus 40-50 years out of Gauntlet.
Ultimately it's up to the storyguide of the saga. But personally I am not a fan of limiting effects like this for some attempt to 'preserve balance' - this is a game about wizards doing epic projects. This is an epic project, and once created such an item may well become the envy of other magi. As a target for a Verditius rival to try and steal or sabotage it sounds ideal.
I'd rather have the player create the item, enjoy the benefit then have it generate some stories than come up with mechanical excuses as to why it might not work. Especially since there's already a canon example.
And since flawless tools are supposed to be tools created beyond what mundane craftsmanship could achieve, how would you otherwise allow flawless tools in your game if not by magic?