Ooo, nice I'm glad LL is finally looking into developing a modern scripting alternative to LSL. Thank you. Lua isn't hard to learn so it probably will be ok for most people, and it is pretty fast and easy to embed. However, everything is a table and they're a bit tedious for some purposes. But, I definitely think scripters will more rapidly develop in Lua than LSL, so thanks for putting effort into moving forward.
While I love Python, it is a bit sluggish as an embedded scripting language.
I would have personally recommended something more along the lines of Javascript since everyone knows JS, it is a very modern language and it performs really well. And, even though it can be insecure on the web... LL would have been able to tighten the VM up on your end you can restrict what it can do. So, I think it would have been a more modern and well established route to go.
And, while there are a lot of naysayers regarding Lua on this thread I personally believe you've made a better choice of at least picking something and moving forward, LSL is too antiquated and limited.
I do hope it is secured properly, however. This kind of move shouldn't be taken lightly, don't forget.