Would you consider adding R3 PgUp, R4 PgDn, please? Based on popularity, I'd say it'd be more worthwhile than, say, 2× 1.5u Code and extra 1u Alt, or numpad 00.
Speaking of PgUp/PgDn, it'd be cool to rearrange the Sign novelties so they can be used as those keys (resembling up/down arrows), for both R2/R3 and R3/R4 setups. Something like this:
Considering the fantasy setting, Super would fit better than Code, imo.
How about Scroll instead of Lock?
R3 \|, R4 <> would be better than R3 #~, R4 \| since the set doesn't have the rest of the UK ISO support.