Um, there's also Memory Tagging which is the topic of this post.
Apple's implemented it as part of the umbrella MIE and eliminates a class of bugs, at least on the surface of their own software, and allows for incremental adoption and doesn't break compatibility with older binaries.
MTE (and PAC before it) store some metadata in previously unused pointer bits, so there are potential issues if you were already using those for something else.
Oh and if your program has memory bugs then you have to fix them of course.
Apple's implemented it as part of the umbrella MIE and eliminates a class of bugs, at least on the surface of their own software, and allows for incremental adoption and doesn't break compatibility with older binaries.