What we came up with for names is rather generic, feel free to adapt for your own liking:
Russia: Ivan (we had the most names for Russia, btw)
UK: AFAIK, it was Steve, not generic I know, but there was a story there.
Japan: I think it was Yoshi, we had a foreign exchange student by that name.
USA: Yossarian-from Catch-22
Anyway, units and abilities:
Ivan’s bravery is such that he inspires his fellow soldiers to berserker status-Ivan and two of his comrades attack at two, defend at three.
Fritz is a tank commander, his Panzer attacks at 5, defends at 3, and takes two hits.
Steve is an amphibious specialist, in amphib attacks he and another inf (coming off the same trans attack at 3. Also, Steve is an expert at avoiding bombardment and may not be killed via bombardment.
Yoshi has an ability similar to Ivan’s-he is an infantry commander. However, he leads his men on banzai attacks, which gives them the ability to attack at 3, but they only defend at one. (All infantry attacking from the same territory as Yoshi)
Yossarian is a bombardier renowned for his desperate attempts to avoid getting killed. (He plans to live forever, or die trying). His bomber, on SBRs only, may roll one die, then choose to roll again and take the higher of the two as damage rolled.
So there it is, a little long perhaps, but the way I see it (all good heroes need to have their story told)