Yes, but there are various accessories that are easily removable even in those first characters. When you don’t feel the pressure to skimp every polygon possible, it can be more productive to create such objects separate of the main body and just stick them onto the final model rather than welding the meshes together.
With Cammy’s default costume, all the belts, buckles, and pouches are separate meshes that were just placed to overlap her base mesh. Cammy’s base model looks fine with them removed, though the base model is a bit bland without them. You can’t just remove her gloves or boots this way, as those replaced her original body parts. The same is true for her green leotard, there is nothing under it. (I wouldn’t be surprised if her green outfit is her original skin mesh, inflated/scaled slightly and then tweaked to clean up issues.)
With Dhalsim’s default costume, it looks like you can remove everything. (I’m looking at the converted models BrutalAce supplied the community some time ago.) Dhalsim consists of a nude base mesh, and every object of his outfit is a separate mesh that has been placed on top of that base mesh. His turban, beard, skull necklace, earrings, bracelets, rope belt, and even his shorts can all be easily removed, and there is still “Dhalsim” underneath them. (No genitalia modeling of course.)
With Rashid’s default costume, you can easily remove his backpack and harness, as well as the bands on his arms, and the loose parts of his top that hang below his belt. You can remove his Dragon Ball scouter. Other items can be removed, as there is still the character’s base model underneath, but they all tend to introduce issues that would require some degree of work to address. His belt hides how his upper and lower body meshes meet. His headgear is removable, but while his head is present underneath, there is obviously no hair modeled under the headgear. His sandals can be easily removed, but the leg straps aren’t, and simply removing his sandals without further changing the mesh should leave him floating slightly above the ground.
So it is possible, to varying degrees, to make “alternate” versions of several of the original outfits just by removing such “removable” accessories. This isn’t uniform, though. Some characters have little that can be so removed, or that you’d want to remove.
Capcom could, if it wanted, go back and retroactively add such features to several outfits. Depending on when they first considered adding costume codes, they could have implemented them from the start.
But that gets back into the reasons why Capcom wouldn’t want to do such a thing. If they’d made alternate versions of only some of the original outfits, players would have complained that the other characters didn’t have similar alternates. As for retroactively adding them, even a little work more than necessary is more work than Capcom is willing to put into the game, and they don’t like to give away for free what they feel they can get away with charging for (even if it is just FM that they charge.)
