Include joint origins at the bottom of baseplates

[antifuchs]

I'd love to have a matching joint origin included in the generated bins and baseplates that allows joining them together easily (especially on the "light" baseplate variant). I have found a set of faces that can be used for this, but they aren't super easy to reach, and I feel like it would be easiest if the baseplate models included a point in the middle of each cutout that matches the bins' base.

My current workflow

Here's what I currently do when I want to join a bin to a baseplate:

1. Select the Join tool
2. On the generated bin's bottom, find a corner peg's angled face and use its center point:
   
3. On the generated base's top, find the matching angled face in the cutout where the corner peg should go:
   
4. Play with the rotation/flip angles if the two components didn't align properly initially (this will result in hilarious clipping if they don't align perfectly at first), but then they should snap together properly:
   

Unfortunately, these angled faces mean you can't select a "slider" join because the angle of motion is off the Z axis, so you can't simulate the ability to pick the bins up straight out of the assembly - they move at a ~45 degree angle, which feels wrong.

What I'd like instead

Instead of this, I'd love if the bins included a joint origin in each cutout's center. The manual steps I'd take for that would be:

1. Select assemble/joint origin

2. Pick "between two faces"

3. Select the two opposing horizontal faces that frame the bottom of the bin cutout:
   

4. Pick the center of the very bottom edge below either of them as the snap origin:
   

5. Select the XY origin as the Z axis, so the blue alignment orientation points up:
   

6. OK, and there's one joint origin:
   

I don't know how to express this workflow in the python API, but it would save me a ton of time for arranging bins in a tidy manner if the add-in could do that automatically.