I am posting each of my suggestions separately. I realise that makes a large number of posts, but it ensures that no suggestion gets lost if there are a lot of comments.
Suggestion 10: A new building type – alchemist shop. Here, for a small fee, you can turn ordinary gems into attack, defence or movement gems. For example, 500 pearls, 500 silver debris, and 500 garnets plus a fee of 1000 coins would give you an attack gem. The ‘transmute’ option in the workshop could be place here as well. Obviously the alchemist shop would require a rather large academy level (maybe 8 or 9) and be expensive to build