How to force print a minimum wall thickness?

I am using an Ender 3 Pro and slicing in Astroprint. I am printing a model of airplane parts. The first part I am printing is the top cap of a main wing spar. It has an airfoil shape cut into the top, so it tapers at the edges. I am doing the cad drawings full size and printing the parts at 6.8% size to get them to fit. I chose to print thin parts in the slicer but, of course, they are coming out like garbage. I switched to a .2mm nozzle and that helped, but it didn't fix it. Is there a setting in the slicer that works similar to:
If line thickness <= (some value) then make line thickness (some minimum value)
Of course I could change the original model, but 1) I want to keep that as accurate as I can and 2) that would be a ROYAL pita.

when you design a part to be 3d printed you have to choose the wall thinkness to divide equally into the extrusion width you plan to use.. if you have a .2 nozzle the the smallest wall thickness you can expect to accurately print wound be .2 Making a nozzle extrude a thread thinner than the opening of the nozzle does not work well. Also tapering does not work well whey you are using FFD fabrication due to the layer on layer function of the process.. You should design the part the proper size, it makes life much simpler.. Also the orientation of the part on the build platform and knowing how the slicer works will help you work around SOME of the FFD short comings, but that takes time and patients.
Good luck!

I understand about designing a part for printability from the get-go. The parts I'm doing aren't really for the act of printing per-say. Printing is further down on the list. I've always liked the airplane and I have the blueprints. I want to hone my cad skills by modeling it full size. "And, by the way, how cool would it be to also print these parts on my printer?" Printing is sort of 3rd in line of priority.

An option of "minimum line thickness" would work for my needs so long as it increases a thin line to a minimum size instead of just leaving it out.