It's a well known fact that while A500 on Minimig core can run at the original speed, A1200 is somewhat faster.
For the most part it is a good thing, but I believe having more control over the core's speed would be beneficial. It could possibly help tackling problems with some of the glitchy/too fast software, as well as simply being a more faithful representation of the original A1200.
Till now I wasn't aware that one of the Minimig's most respected devs, robinson5, has been actively working on
tackling this issue on the MiST / SiDi side of things. His current iteration of the core has a toggle with several speed settings. While not cycle-exact, one of them can bring the A1200 much closer to the original 14Mhz speed. You can read more about it here.
Here's hoping this can be eventually implemented in the MiSTer's version of Minimig.