As long as made-up stuff is cleverly done, it should work out pretty well, I think.

I really like this particular DLC, and not just because of national bias - it really makes a Poland playthrough an interesting prospect, and adds much needed flavour to ahistorical games.
I do hope some of the naming suggestions make it in eventually, though! It is incredibly weird seeing a 37-tonne light tank next ot a 14-tonne medium and 32-tonne heavy tanks.
So, 8TP would work better ? or say Ryś (Lynx?) maybe?
FWIW, naming early Polish tanks should be easy - just see how much comparable historical tanks weighed and base the name on that.
For example, if the 14TP medium tank is supposed to be comparable to the Crusader tank (as it seems Poland is supposed to emulate the UK cruiser tank design path?), then it can be renamed to 19TP, since the Crusader weighed ~19 tonnes.
So if the pinnacle light tank is comparable to the Panzer II Ausf. L "Luchs", which weighed ~12 tonnes, then 12TP or thereabouts is a good potential name.
Also, no jet aircraft or halftrack names? Or did you leave them out as a surprise?
