Nice concept! Some thoughts:

• I like the easy AltGr placement! It's as practical as the Wide mod on a standard keyboard.
• The Enter key should've been straight – you're not going to hit that narrow strip anyway
• I'd consider fixing the left-hand row stagger, like a milder version of the Angle mod but in hardware! It's really worth it for the wrists.
• I'd split up the CapsLock and/or Left Shift key, making the left part (one key wide) the CapsLock itself and the inner part an Extend/Fn key!
• Hitting BackSpace and Delete all the way up there looks risky? Maybe split the Enter key too, putting Back right outside Enter?
• You're missing a Menu key? I use it (but the Extend version which is easier to hit). In Linux, I use it as the Compose key.

I like the compactness, and also having lots of keys on the bottom row. But in that case I would remap them as having punctuation there is a bit of a waste IMO - I think they would be crying out to be made modifiers via thumbs - Shift, Control, Alt, Extend even. And of course us ISO users would be still needing an extra key next to the Z. Better still, go the whole hog and make it fully symmetrical :)

Here's an image I once made to show my suggested row stagger:

In hindsight, I don't like the AltGr placement on that board. Too far to the right. Ah well. Not sure how single-width Space keys (one on each side) would work – okay, or too hard to hit? Maybe okay since the thumbs would be resting on them. They could have some sort of homing nubs too, being home position keys. Another possibility would be to add half a key width to the middle, making the 6 key 1.5 normal keys wide etc.