Do not waste any time waiting for this (font property control) to be added to SketchUp Text leader objects (most especially by this coming fall.)
This thread is 5 years old, and in it I previously mention that text property control had been requested numerous times over 7 years prior to that.
I believe that the developers of SketchUp have a policy on LayOut being the professional presentation application for SketchUp models, and so have concentrated coding efforts at dimensions and callouts for LayOut documents rather than the 3D .skp
files.
That being said, the SketchUp C API does have font control for leaders and dimensions exposed, however the C API is still (as of this writing) only read-only for live models.
You might find a workaround by having a library of text leader components with various properties, and insert them via code, then explode them and attach to objects, tweak the leader vector, etc.
(But as you noted, currently the alignment seems to be hard-coded.)
Be aware that SketchUp model Text leader objects are rudimentary callouts that exist in 3D model space.
LayOut Label objects are full featured callouts that exist in 2D paper space.
So for complex engineering documents, prefer 2D paper space dimensions and callouts, which do have font property control accessible via the Ruby and C APIs.
See:
Could Layout Labels be set before going to Layout ?
Yes if your code is using the LayOut API to create or modify the .layout
file in which the labels will exist.
It might also be possible to use SketchUp Text leader objects as a sort of boilerplate for later LayOut Label objects. Meaning, that the code would read the Text objects (probably using C API read-only calls) to generate the LayOut Label objects (if you wanted the LO labels to get their font settings from the model text objects.)
The code could also override these font properties for other global font settings.
I’d envision that the model viewports in the resultant LayOut document would then have the layer/tag switched off that the model leader objects use, so they do not show in the LayOut document.