I would like to see in Lua :
1/ As I discussed several times : Thread safe State sharing. For the moment, or you have to "send" bytecode among threads or use a lock mechanism which seem to penalize by a large amount performances. I would like to have an option at compile time enabling thread safe Lua, having out of the box transparent semaphore locking on global objects. Something efficient, easy :)
2/ yes, I'm missing compactness of C compoundeds operator like += *= :? and so on ... something suggested it seems several times on this list but seems always disdained by gurus.