I don't see what any of this has to do with purported ITRANS/Optitrans standards or who wrote what file. It's simply about not adding idiosyncratic characters to the central copy of the file.
Satish needs to input « », Vasuki needs to input →, a lot of other users might need to input other special characters. There is no way to balance all these idiosyncratic requirements in a single input method.
The fact that the proposed character is used by the community of Sanskrit students doesn't invalidate this argument; there are plenty of field-specific symbols used by English-speaking mathematicians, linguists, architects, engineers, cartographers etc, but no English input method tries to accommodate all these symbols, nor is it expected to.
Users who really need to input idiosyncratic characters can always use the associated Compose key sequence. Of course, they can also modify their .mim files individually, but non-technical users might hesitate to do that.