I’m bored and I’ve got nothing better to do,so here’s some possible event vehicles for every nation
Ki-44-II Otsu
a tank hunter plane like the hurricane mk4 having cannons of the same caliber.this one should go to BR2 because it has 12.7mms instead of 7.7mms on the hurricane,and could have dual 100kg bombs.
BF 109 E7
almost identical to the 109 E7/U2 in game,leased from German to Japan in small numbers,but never really caught on.although ordinance was not provided for these planes,DF could maybe do some historical alteration as they are famous for and give it japanese 50kgs bombs or something (I don’t know if the german 50kg bomb rack could fit japanese bombs,I doubt it though),but I doubt they would do this.Either way,it would still be a fun edition,basically a zero with better guns at a BR lower but (most likely) no payload.
Ke-Nu
a Ha-Go but with the improved 57mm cannon on the Chi-Ha,would be a nice BR1 addition
AEC Mk2
a fast little car thing armed with a slight improvement of the pretty good british 57mm cannon,good fit at BR2
Light AA Mk1
4 BESAs put on a light tank chassis,sounds like good fun at BR1
M2
a bunch of guns thrown together,with 9 MGs (although 4 are fixed,2 don’t shoot and are probably replacement MGs,and the other 2 face backwards) and a 37mm cannon,ideally at BR1
Neubaufahrzeug
A prototype tank (this one actually saw some use in Norway,although limited).this tank has only 10mms of armour on average,so a very very easily killable tank which is a very limiting factor,but there are quite a few unique things about this tank that could justify it’s addition.it has multiple turrets like the T28,although one of the MG turrets faces the front and the other faces the back (they could possibly make this one AI controlled like on the LVT4).the main selling point is the short 75mm and 37mm in the turret,which is quite unique in a tank,although the 37mm won’t have much power to it.The machine guns in the tank are unique as well,as the are MG13s with lower ROFs then the MG34 (so it overheats slower) and uses 75 round drum magazines (that should load faster then belt fed MGs because…it’s just common sense).this could go to BR1 or 2 depending on the shell loadout for the 75mm,if it gets APHE and HE it should go to BR1 (standard shell loadout for short 75s,maybe throw in some HEAT rounds as well 
),but if it gets put in BR2 it should get HEAT and HE.This tank is comparable to the Grant in the sense of having a 75mm and 37mm,but heavily lacks in armour and penetration.
Sd.Kfz 251/10
this could be a fun APC to have at BR1 armed with only a weak 37mm.(I don’t think any APC should be higher then BR1 unless it has a good cannon like the Sd.Kfz 251/9).Casemate,bad cannon,limited ammo,and no MG (all things early panzer 3s do better for the most part,being turreted,much more ammo,and two MG34s) can help justify this being BR1.
Sd.Kfz 234/1
the original version of the puma,armed with a 10 round 20mm cannon as the primary armament,this could fit into BR1 well.
SMK
A KV1 and a T70 slapped together (keeping both turrets and having a similar armour value to the existing KV1),seems to be something unique at BR3
SU-76D
Something that would preform similarly to the StuG,using the 76mm cannon with decent penetration,BR3 seems okay for this
GAZ-AAA 4M
the ultimate milk truck experience,a huge volume of fire assures fun at BR1
hmm
