It would be really nice to have the a colonist able to craft a large number of possibly complicated recipes.

Things like:
All those fiddly medieval wall pieces
Shingles
Stairs, fences, slabs, and so forth, in several different material types
Torches, item frames, armor stands, and any number of semi-rarely used components
Intermediate items such as sticks

The builder just doesn't have enough recipe slots to cut it, and can't craft 3x3 recipes in any case.

3x3 crafting has been planned for a while and will come with a range of workers to fit all crafting cases, the system is ready but it still needs to be implemented with the request system properly.