What is the problem to move some of the symbols on the same row the space is? I know this last row is not drawn by vkbrenderer, but by the upper layer, so what? we have both sources so it shouldn't be a problem to have different layout for landscape/portrait. Also keep in mind languages with more than 28 letters in their alphabet.

Otherwise what you've achieved looks pretty good.

EDIT:

A wild idea:

Add another property to vkbrenderer class, lets name it "keys-special", which contains an array of chars. For every char in that array, create a button (from him-western-...) right to the spacebar. Treat those buttons the same way space button is treated. That way ABI will be kept, i.e. if vkbrenderer class does not expose such property, do nothing. I hope you got the idea, I can elaborate if needed.