Yeah the head is terrible, I meant we needed to actually make a custom head first, by attempting to sprite over it. But I had no luck when I've tried, I can't scratch sprite or edit like that.  I don't think just head swapping is going to workthou.  This is why I was trying the other head originally, I think he should look more like a rabbit and less like bugs bunny. ;D
If we can make some custom heads then we should be right, maybe we can dig up some black and white images of Usagi and create some heads that way.
Edit: Here's a very quick attempt, but I stuffed up and made it too small at first and had to enlarge it again to test adding it to the sprite.  But if it's done properly and with more care, we will have heads the right size to use.  Also will need to spend more time finding source images.
Sourced a head, converted to indexed and reduced the colours to only a few (like 4).
Reduced size and edited head (I had to redraw many pixels)
Reduced size and edited head , second stage
Head Resized and added (My bad I made it too small to start off)
Head edited again.
These are just rough examples, but I'm not really good at this sort of thing anyway.  But you can see it's not that hard, someone with more experience converting sketches to sprites could get it perfect.
Anyhow I'm not worried about him for now, I'm just concentrating on editing the foot soldiers.  I definitely want to add Usagi, but he will have to wait.
EDIT2 - The base is a hard choice, the clothes are slightly different and there's also deciding two swords or one.  I think we will still might have size issues too because Usagi is supposed to be pretty short.