would that fix the small space bar?)
The small spacebar doesn't need to be fixed: it's the greatest feature of the HHKB Pro JP. I'm using an HHKB Pro JP even though I don't speak japanese whatsoever: this makes the keys at the left and right of the space bar easier to reach with your thumbs. It's also make for more modifiers. So instead of a regular keyboard's ctrl+alt+shift/meta I've got ctr+alt+shift/meta+hyper+super... With Topre switches.
There are, IMHO, superior custom physical layouts out there made by some here (like split keyboard with tiny spacebars and easy to reach modifiers) but... They don't have Topre switches. So it's HHKB Pro JP for me.
As the arrows key cluster: I rarely use it, I've got mod+{i,j,k,l} to "move the cursor".