It would take a varying amount of time for any other importer to import a model with smoothing groups, and while it increases import time to import the entire rest of a model, as well as splitting the faces on import, i'd be fine with that

For example, i have a Darth Vader model i want to edit that has 99 bones, 23,358 polygons, and about 23 materials, and is a total of 7.22 MB, importing it with custom normals only took 14.4 seconds

Blender has several other import options that can correctly import a model's normals, but those don't support armature, why is it that much of a problem to get proper normals with SMDs? They have all that data for each polygon in them, i'm sure it's not easy, but wouldn't there be a way to compare the normal data per-face and just split the edges wherever the values don't match?

And while i could just manually do edge splits, that would waste a TON more of one's time than just waiting about 5 or so extra seconds when importing

It's a 23k polygon model with so many nooks, crannies, and tiny doohickies, to use your method and search out all the sharp edges on this blob of a model would take a long time

I did a similar thing with the Master Chief model from Halo 3 and that took a while, but that model only has 5,066 polygons, so that was actually easy to do, it was just a little time consuming

Currently, when you import an SMD with custom normals, the model has it's smoothing groups intact, but at the cost of splitting apart each and every polygon in the model, which can make it very difficult to edit (which is what the tooltip warns you of), but it also causes the model's polygons to triangulate while the bones animate, and this shows up in the Source Engine, so this method of importing custom normals is almost not even worth using, IMO

So my suggestion, if it's even possible, is instead of splitting up each and every polygon, would it be possible to either
or
And when i say "splitting the edges", i mean like when you have edges selected, you press Ctrl + E and you select 'Split Edges' to separate the polygons via selected edges

Because having the edges of every polygon split apart makes it impossible to select multiple faces that are connected, and the triangulation while animating looks horrific