Obviously, Vote #1/#2 Daniel Slechta’s answer to Could emoticons form the script of a new constructed language? and Daniel Ross’ answer to Could emoticons form the script of a new constructed language?
(I disagree with Daniel Ross’ first point, that the emoji must be conventional and not iconic for them to be a language at all. I think the real issue is his second point, that icons can only go so far.)
(I will hold my tongue about Esperanto diacritics, because I otherwise like Daniel. ;^)
My concern, as expressed in that question, is what your verbs and syntax are going to look like, if your emoji-based language is not going to be just some rebus—or, as Daniel Slechta argues, extremely restricted in what it can talk about.
The challenge has been addressed in an actual symbol-based universal constructed language, Blissymbols. But I don’t think anyone would argue that Blissymbols’ verbs are intuitive.