2.3 includes the new import option.

Are you exporting an animation? All bones are exported in that case, as it's not possible to tell whether a mesh somewhere, potentially in a totally different file, uses them as bone parents.

This shouldn't be a problem in-game as studimdl will automatically cull bones that aren't used in the compiled model.

That should be happening already. I'll look into it tonight. Is this a DMX export?

Source doesn't support scaling. You'll need to redo the animation without it. Sorry!

No. You'd be looking at writing your own comparison system from scratch.

What you could try doing is hacking the VTA. Try replacing frame 0 with the reference mesh. There will be a bit of processing required; see the spec.

Your $cdmaterials command points to models\props\ramp, which should be a folder ("cd" means "change directory"). Your $basetexture parameter also points to models\props\ramp, which should be a VTF file.

One of those is wrong. :)

QC and VMT please.

Make sure that your QC file is the last thing given in the command. It seems that currently "-h" is. Other than that I've no idea - this is nothing to do with Blender.

The Source 2 limit is four weights per vertex. The compiler will cull anything over that and issue a warning as appropriate.

Aside from the difficulty of working out the edge of the selection (which would be very slow in Python), you'd have exactly the same problem as trying to do it over the whole model. Just with harder-to-spot errors. :)

Since this only affects a handful of files in a legacy format, I suspect that manual fix-up is the best solution you're going to get.