I sympathize with the goal but accessibility benefits would be far outweighed by maintaince costs. We regularly use grep to find code which is about to be deprecated; wikis copy gadgets from each other; more experienced developers are sometimes asked to help a wiki where the local maintainers have less experience. We have a whole global user group for people who go from wiki to wiki and fix things.
And that's not even taking into account the implementation costs, which would probably be massive if it includes stuff like localizing Lua/Javascript language keywords. The Wikimedia community collectively has a lot of experience with web development but not a whole lot of experience with programming language compiler development.