In my opinion this adds a fair bit of new complexity to the composer, and the marginal benefit of slightly less translated text – since we already have that text area reserved at the bottom – is not worth it.
It’s arguably a worse UI, since the words are fairly clear and help identify the floating area on the right. Take that away and you make the UI less clear. What is that area on the right?
In summary, I would be quite opposed to this change.