Are there any limitations on building and repairing objects like there are in Pathfinder; specifically, in regards to daily limits?
Am I limited to crafting a single rifle, grenade, suit of armor, or fusion, in a day, for example?
Per the Engineering skill entry, there does not seem to be a limit on repairing multiple items in a day, or repairing one item multiple times a day.
From my recall of crafting rules, which I may be conflating with Profession skills, you'll probably find it difficult to complete work on a single item in a day, let along multiple projects.
You can craft most things in 4 hours or less. Only really large objects (such as vehicles) really risk taking longer than a day.