A great dio, the figures are excellent, particularly the medic (though where are the red X's on his helmet?).
Also nice to see a 251 done well and in 'ambulance colours', is this the Tamiya kit?
the groundwork is also very good but if im honest, I don't like the way the 251's front wheels are hanging in mid air, i'd like to have seen a bigger base that would have fitted the entire half track on. Although I presume this is what you mean by 'breaking the rules of diorama building' and I can't knock you for trying.
Overall a great little scene, well done,
James