Given that the tree actually looks pretty good using default normals (and a bit weird in the picture above), I'm considering calculating the vertex normals shown immediately above at runtime (unless I find a way to use a UVW channel to store them) so that the default normals and these normals can be used in conjunction with one another. I don't *think* averaging the two will work, but I may try that too.
I'm hoping to make a couple more trees using these branches. This one was intended to be a largish tree, but has come out pretty small/medium-sized, so I'm looking to make a larger one, a young sapling and a shrub-like version (may not look believable but worth a shot and might save me making an entirely new shrub). I may try using speedtree to make the variations to save me time.