[ygra]

If this is merely an input method then MathML is pretty much all you probably need as it can be pasted into or consumed by most applications handling math, including Word. Plus TeX for, well, TeX.

This format is mostly geared towards input as well, in that you have defined automatic replacements as well as a format that can be typed easily and be built up to rendered math during typing. If you have your own completely different input method you wouldn't gain much from this.