Similar to effect device position change option:
Two buttons, and/or drag and drop to change the order of Macros:
Because while programming macros, one would like to set similar macro controls besides each other. But this is not always a first priority while doing creative stuff.
Note: it might be a good idea to rename default macro names like “Macro 1” after reordering. Or always prepend “Macro X” to the begininng of the name and change that accordingly.
And please, expandable macros 
8, 16, 24, 32
Yes. Because rows can stack vertically in sampler and instr. properties as long as the number is doubled. And Instr. macros can expand like any other plugin that expands horizontally.
There’s likely room for 16 across on most monitors, too. Lots of unused space in the macros gui. I like the idea of expandable/collapsible sections in the instrument editor
There is also nothing wrong with having pages of macros if things do not fit. Since Redux doesn’t allow to automate native effect parameters, being able to control more than merely 8 things would be a welcomed addition (although I still wish for phrases to automate things, desperately).
Drag and drop macro reordering would be nice to have indeed. It would greatly simplify control remapping when Renoise is being controlled externally, i.e. by using /renoise/song/instrument/-1/macro<N> OSC command, without having to manually reassign device parameters to different macro controls.