How could the language be made as easy as possible to learn coming from any linguistic background? How could interest in the language be fostered in as many people as possible?
The problem is, people don't want language to work that way. It's not specifically that they want it to be hard to learn, but they want a language with nuance and ambiguity. We like puns and plays on words.
There's also an argument made by some rhetoricians that ambiguity in language (and other places) allows people to break prisoner's dilemma-type games, and we do so constantly as lubrication for our interactions. A simple example: you get a speeding ticket. You can pay the ticket, you can attempt to bribe the officer to not give you a ticket, at tremendous risk if it fails, or you can make an ambiguous statement like "is there some way I can just pay the fine right now and get on my way?" that an honest cop will answer 'no' and you end up having to pay the ticket, but there isn't sufficient information there to successfully accuse you of bribery, whereas a dishonest cop will take the offer. You reduce your risk/reward ratio through ambiguity. The same strategy when applied to relationships is even more successful because they're iterative.
Our communication is inextricably interwoven with ambiguity, so we will invent it out of need if we don't have it.