I will suggest a small add-on of a unit (to the red/green/blue OOB)
Its the Danish motorcycle NIMBUS mounted with the 20 mm Madsen AT gun.
it was usen againts the Germans when Denmark was overrun in one day April 9'th 1940 and the remaining units was captured by the Germans and propably used in Norway and/or the east front.
This very mobile unit with a punch could be fun to have.
(Actually it was also used as an AA gun but in a different version)
In the AT role it could be fired both from the MC and removed from the MC.)
The photo from this page
http://www.milhist.dk/vaaben/systeme...s_oversigt.htm