Memory is not a factor.I agree.
Software wise there should be no real reason.
Unless of course Apple use an excuse of limited memory which does not allow this to happen on the 1st watch.
If we feel the design is nice so far. Really all they could do it minimise the bezel, but Apple are not known for doing that.
So I would imagine it would be more internal specs/speed/memory with perhaps another sensor or more accurate one.
Not a LOT else you can do.
The watch face just loads some image assets, hardly a huge memory draw.
The only watch faces that could draw a lot of memory are truly 'animated' watch faces, with constant transitions or changing/shifting elements.
There is technically no reason why apple cannot allow simple static asset watch faces.
I'd like to see some fancier faces, as well as some geekier ones like binary, flip clock, polar clock etc.
I'd also like them to allow a grid of complications over the whole watch face, and let us choose what we want, and where we want them placed.