It looks like Nokia Audio Suite can be used as an XMF editor. However this product was found only on discs supplied with some Nokia phones. Several years ago I found a guy that had such a disc and uploaded the product for me but I could not activate it because the activation is done through the Forum Nokia resource that was already down.

I saw this last night , I did a check today on what I thought would resolve the matter, it comes at it from another angle but specs you listed are met, if you can give me a summary of the projects desired outcome and the full list of software that would allow you to achieve these unhindered with no workarounds, think ahead a couple of years if there are aspirations beyond those mentioned above