It all boils down to a question of agency. Languages don't promote anything. The English language encourages a sort of forgetfulness, which we have even seen fit to give a pair of technical names: metonymy and synecdoche. The former means to identify something by referring to one of its parts; the latter means to identify a part of something by referring to the whole. Rhetorical devices are no excuse, however, for intellectual laziness.
If you ask the question, Could a new phonetic alphabet promote world peace? what you are actually asking about is whether people will be able to use this new alphabet to promote world peace. Alphabets have no existence apart form language users. Alphabets have no agency apart from language users, and in the strict sense of the term, they have no agency at all. The part only functions as part of a whole. So the answer to the question is: No, absolutely not. Only language users, living breathing human beings, can promote world peace.
My criticism may appear rather paltry, even inconsequentially nit-picky. Though I believe it an important point to make. Contemporary post-structuralist theorists tend to think of language as being determinative to how people understand their world. Change the language, this line of thinking goes, and you change how a person understands their world.
Certainly language shapes how we understand their world; but it's not a determinative one-way street beginning with language and ending with how people think. Language users like ourselves shape language, just as much as our thought patterns are shaped by language. The relation between language and language user is one of dependence. No part without a whole; nor any whole without parts.
Like the 20th century attempt to create a universal language named Esperanto, these new attempts will get us no closer to the goal of world peace. They may, in fact, take us further away. If we suppose a common language will ameliorate violent behavior, like bread can ameliorate hunger, we will have misunderstood the nature of violence.
For the nature of violence also boils down to a question of agency, mine and yours, ours and theirs. People may communicate with and understand each other perfectly. That's not stopping them from also wishing the most unspeakable horrors descend upon the other person.
And world peace? "I can certainly see the argument for saying that a shared language can prevent conflict. However, shared language can dupe us into thinking we share other things - values, beliefs, goals - when in many cases we don't. Does it minimize differences, or merely mask them?Though it may seem rather immodest of me to say so, I am quite sure it does not.
"In any case I'm not sure that ease of communication guarantees harmonious communication."