Would a universal language be symbolic?

There have been a few proposals for symbolic universal language, most of them taking their inspiration from Chinese ideographic systems.

• Pasigraphy was at the start of the universal language movement: they were akin to universal thesauruses in symbolic form. Rather naive in retrospect.
• Blissymbols was probably the most thorough recent effort, and it has found some unexpected usage since for teaching communication to language-disabled children.
• iConji seems to be some sort of mix of Emoji and dingbats.
• And of course there’s Emoji themselves, which are increasingly being used in communication, though of either a more rebus-like or a less syntactic nature.

There are pros and cons to symbols as a universal language. Some symbols are arguably more iconic or indexical as signs than words, and less arbitrary, so they should be easier to learn. In theory. In practice, the minute you move away from concrete nouns, the signs symbolic languages use look pretty arbitrary; and even if they are conceived of as indexical, the metaphors may not be all that obvious. I’m not convinced the gains in iconicity would really be worth it.