Unless someone takes over MDX development, it appears that MDX will no longer work in mIRC 7+. I'd recommend switching to DCX as it can do most (probably all) that MDX can do and is still updated.

As for nicklust, if it's still updated, then the next version will probably work with mIRC 7+... just ask them.

As mentioned, DLLs and scripts that stop working when mIRC gets updated need to be fixed themselves. It's not up to mIRC to guarantee compatibility with DLLs or scripts.