| I like the idea of the bio-tech warden. If you where going for a sci-fi feel, that would be perfect, but it might not work well as steampunk fantasy-tech (unless the warden had found a way to bond with a number of symbiotic organisms).
Thinking about it, the barbarian could work quite well with sybiotic bio-tech, albeit of a more offensive/unstable nature.
A druid could also be explained away in a bio-tech fasion, but the change would be less dramatic, and more sci-fi than fantasy.
Shamans, in my opionion, would be harder to to as a bio-class, and easier to explain as a psychic or nanno-tech-based one.
Interestingly, the best fit for divine classes would probably be as futuristic psychics... Go figure! (or alternativley, it could be powers given to them by trans-dimensional beings/forces that nobody is sure exist. As far as we can tell, their powers seem to come from applying extreme modifications to the quantum probability matrix... Perhaps that end description is actually a better fit for what psionics is turning out to be..)
That's all high-tech sci-fi though (which is fine if that's what you're looking for)
For the Sorcerer re-theme, I'd simply draw on the traditional difference between sorcerers and wizards. While a gadgeteer gains their understanding through years of study and constant experiementation, the Tech-sorcerer is a Scientific Savant, intrinsically understanding the underlying forces of the universe, and mixing and maipulating them as an artist would turn clay or paint into an artwork.
A Scientific Savant caries feuls, chemicals and stored energies, and mixes them on the fly, coming up with strange and sometimes frightening results. Simply make two different builds: one for Dex-based, and one for Str-based Scientific Savants. | 
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