To SSJ4 Furanki: (Sorry, I don't know how to properly use visitor messages)
DISCLAIMER: I'm not trying to be mean with the following comments, they're just constructive criticism. Art isn't for everyone, and what you've shown in the other departments is proof enough of your skills.
Well, I guess that's the idea I had with Red. But now his right arm looks a bit stiff. And his face...it's a bit...derpy. Just the way his eyes are in comparison to his mouth. The Green/Leaf sprite is another improvement, but it still doesn't look like it's at the same quality as the HG/SS sprites. I think at this point it might be better to find a spriter. But, before you consider that, read the rest please!
I just mentioned the Sabrina sprite because of how different it was to the original art compared to the other sprites. Technically you could find little nagging problems with all of the sprites. Like with Blue, there seems something different about him in his HG/SS sprite, but I can't put my finger on it. What I'm trying to say with that is that it isn't necessary to change Sabrina's sprite just for that. Her HG/SS sprite is still recognizably her, perhaps just a bit modernized.
If anything, I think the issue you'll run into with the HG/SS trainer sprites is that all the sprites that you don't change are going to be a lot smaller in comparison. Also, all the Pokémon sprites will be off in size by comparison, especially when you compare sizes in the Pokédex. Obviously you can't import all the DS sprites because several of them won't fit within the GBA's 64 x 64 pixel limit, and using shrunk versions of them defeats the entire purpose of using larger trainer sprites.
So, I guess the big question is...Is it really worth it to change the trainer sprites from their FR/LG versions if it's going to lead to that many issues? I'll let you answer that yourself!