I have been testing this with 16x16px tiles, and yeah, the tileset shrinks! So you can just take the same images, downscale them to one third of their size so pixels are 1x1, and it will work the same. The number of available tiles will be the same no matter the tile size. Same thing with character sheets, you can just take a regular character sheet and downscale it to one third of its size and it will work fine with the 16x16 grid.

For compatibility purposes, I'd recommend keeping the triple size version in your asset packs (since most people will stick to the default 48x48px tile sizes) and also add a 16x16 version for the people who'll use a native 16x16px grid.

Hope this helps. Thanks for your work! <3

I used MZ 1.5.0 for testing.

Yes, if you change the tileset size to 16x16 then the overall block size will be reduced (by a third). But the character size does not change.

I hope this information helps you.

I don't own MZ but I'm familiar with plugins for RPG Maker that change the tile size, it's likely that MZ works the same way.  The sheet size would be smaller, the number of tiles per sheet stays the same.  As for the B tile needing the first square blank, it's a quirk of how RM's programming for passability works.  Think of it as if that tile is what's filling in that layer unless replaced by a different tile.

Since RPG Maker MZ release, You can use same size tileset from MV for use MZ but one thing only Tileset B maybe problem in first spot I don't know why.

But don't worry about other section tileset because all working except Tileset B only.

So you don't worry :) I think some dev need to manual arrange them before use on own games

I tested on RPG Maker MZ Ver.1.5.0