I do still love GF Soundwave, but he's kind of ruined by a factory error that makes transforming him a horrible, thankless task. As TFWiki says: I know pretty much zilch about customising and all that stuff, so throw this to the gallery - can this be fixed? If so, how?
Do you have the figure, or are you interested in purchasing one? From your phrasing, it sound like you have one in hand. Luckily, there are a couple of ways I could see about doing a fix. They are both challenging, but the first option is to find a junker Cybertron Soundwave, as the plastic colors look to be identical, and swap out the parts. You'd be unscrewing the legs, as well as the back plate, and then transplanting them. If the plastic colors are not identical, you might have to remove one or more pins. This is a tutorial with a couple of options:http://www.tfw2005.com/boards/tutorials-how-tos/214537-how-remove-pins-rivets.html It should be fairly simple to realign the parts once the pins are out, if I'm understanding your problem correctly. Fair warning, removing the pins runs the risk of breaking a part. Although, even if the issue is common, you're the only person on the internet who is talking about it.
So I just performed this operation tonight. It was... not fun. The plastic colours are not identical; Hasbro uses a brighter blue, and Takara uses a darker gray. The offending piece on the Takara mold is the back of the crotch/pelvis, where the pinhole is at an angle. Ideally, you can just swap that piece. But this requires multiple pins to be removed, some of which (namely, the gray "stem" pieces that connect his back to his pelvis) are rather long and were very much designed to go in once and then never ever come out again. You can't just push them out from one end; they have flat heads on the outside and are heavily threaded in the inside. The way I managed to do it (without a soldering iron, which I don't have) was honestly to use plastic sprue cutters to just mutilate the plastic on the Hasbro version's back and Takara version's butt so I could remove the pins. I mean I went to town on those areas; completely destroyed them. I initially tried to remove the pins, but ended up breaking one off in such a way that it was nearly impossible to get the rest of it out. I also used a small hand drill to drill small holes directly next to the pins where I needed to preserve the plastic around them (Hasbro pelvis and Takara back). This allowed the pins to have enough wiggle room to be coaxed out with only moderate violence. In the end, I did break one of the stem pieces, leaving my final figure with two different shades of gray between those two pieces, but I didn't much care. Overall, it was a frustrating endeavor, but I now have a fully transformable Galaxy Force Soundwave. And a fully destroyed Hasbro version.
Yikes... That sounds considerably out of my league. I'm glad you managed it, but perhaps I ought to finally let this dream die.