I'm not saying it could not be done.
I'm saying -- I don't understand the value, and don't think a watch can be made to operate like a phone does.
I see smart watches as *companion* devices to *phones*.
And then when you say that Gmail shows *complete mail*:
- What happens if message text is 50 kilobytes? 100 kilobytes? 500 kilobytes?
- What happens if message text has formatting? Bold, italic, font sizes? Tables?
- What happens if message text uses "responsive markup" (CSS media queries, based on screen size)?
Oh wait, Gmail ignores CSS media queries, but speaking of AquaMail -- should message text be fitted to the phone screen's width? to the watch's width (probably making it unreadable)?
- What happens if message text has embedded / linked images?
In view of the above, do you still think that a smart watch is just like a phone only smaller (but who cares, you have good eyesight)?