I have no doubt that the curse that created them come from the same source, and that they're two very similar creatures. Both of their forms are heavily decayed or outright emaciated. You bring up a good point that the Cursed Bokoblins likely are the predecessors to the Redead (this wouldn't surprise me at all, actually), but the chances of them changing from one to the other is rather slim. Beyond the idea that they are undead and were created from a curse, I don't really see much of a relation between them.
Your concern is essentially answered in the various sections below:
So you think that the ReDeads are the Cursed Bokoblins and that the physical changes are the result of decomposition? That doesn't make much sense.
I was struggling to come up with the right term, but decomposition kept rising to the top. I basically meant the overall decay that time affected as it went from Skyward Sword's era to Ocarina of Time/Majora's Mask, and so on—cellular deterioration, if you will. The skin of the Cursed Bokoblins became a brown shriveling rug that covered their bones, their faces became "wooden" masks, and the hair and horns fell off, although the eventual Redeads maintained their physical structure.
For one, the ReDeads are taller. Decomposition can't do that. The ReDeads have a totally different physical structure too. Decomposition is a deterioration of the body but for the Cursed Bokoblins to become ReDeads they would need to grow in various ways. That just can't happen over time because they are dead.
Living underground can change an organism's physique over time but getting taller would not be one of those changes. Anyway, that process is evolution which dead things aren't capable of.
To me, this is where the emaciation comes in, although it I could be biologically wrong on this. I'm just thinking about becoming taller as they develop a scrawnier frame; not all things are tall and skinny necessarily, but Redeads are both of those. Another thing is that they're undead. Now, I'm prone to think that this means they're bodies aren't alive in any way which would also stymie cell growth), and that the evil magic is all that's keeping them mobile, but I also like surmising that the "curse" is not only what makes them move, but grow as well.
Both of these are things I can't validate, but I think the hypothetical curse justifies the explanation for them.
As well as that, ReDeads appear in several different forms. The Wind Waker ones are completely different to the Ocarina of Time/Majora's Mask ones and the Twilight Princess ReDeads are also totally different.
I don't know. Overall, I believe Nintendo has stuck pretty close to how the Redead/Zombokoblin designs correlate.
Wind Waker - Recall that
these Redeads are found in coffins in this game. The enclosed space might have caused their bodies to not deteriorate or emaciate, but stay closer to the Bokoblin side of things. Contrary to OoT Redeads, WW's had a gray complexion instead of the original taupe, and they're almost more elephantine—just look at the ears—which tells me that they stuck to the Bokoblin side of things. Their predecessors could also have placed their undead bodies in coffins to ward off unwanted intruders in Dungeons and such.
Twilight Princess - And
here the TP Redeads are wrapped in bandages. Now, this is later on down the timeline, so it's possible that the decomposition really begins at this point (as well as the curse's curative effects). They wear bandages so that their bodies don't deteriorate as quickly. That, or they were used to guard the prison known as Arbiter's Ground and were patched up as they lay dying from some huge revolt. I like to think the former suits this explanation better.
Not all ReDeads live underground either and there are several cows found underground too which means there's not a complete lack of food down there, but now I'm just being facetious.
Really can't argue with that.
Sorry if I've misunderstood what you're saying but it just souds incredibly unlikely that the Cursed Bokoblins could ever actually be the ReDeads.
Yes, both enemies being created as a result of the same or a very similar curse is likely, but for them to actually be the same bodies strikes me as too far-fetched.
This is really just an attempt at branching this theory out a little more. Original hypotheses happen to be far-fetched a lot, but that's what makes seeking the end results seemingly worthwhile. Already more things came to mind because you prompted me to think about them better. In reality I'm not particularly good at theorizing—or rather, theorizing and backing it up sensibly. So thanks for putting up this challenge. x3