For small parts like you mention, 3D printing can be a good solution.
I heard it has some issues (almost all printers do), but the da Vinci 1.0 AiO has an integrated 3D scanner and fair build volume and price tag so looks like a good one to begin with.

Think of a layered part more like wood than plastic, structurally. It can break across the seams. So for structural parts carrying heavy loads you need additional solutions like conjoining parts with different layer orientations or epoxy reinforcement. For other parts, ABS is structurally good but not so good against fuels and UV radiation. You can have nylon parts produced through SLS processes at 3rd party services like Shapeways. It allows sizes over 2' with high accuracy and strong parts but the prices will be very steep and nylon is far from great for outdoor use. A good option will be printing in PET because it is resistant against most chemicals and weathering.

You can also think of printing larger parts for molds, in many sections. Then they will be usable for hand layup of exterior parts. Silicone casting in simple 3D printed molds works great as well. Always consider there is some manual labor involved - cleaning the print, filing, smoothening. So if you have a lot of extra time or have parts that need to be replaced in batches, 3D printing will be a solution.