Yeah, thanks.

Or one could use it's boardgame's version here as well (as a mod):
viewtopic.php?t=70800
Ok, so we find there the same kind of folders as mentionned before, in my previous post... But this doesn't tell us where to find the same kind of information in the folder system of the vanilla game.
For example, it seems that one could just modify the
units.csv to add snipers to basically all factions -
which is not a bad idea at all, by the way* - using the "model" of the japanese one (and thus "calling" it for each one of those "new" units); it seems that it has beem done this way in the Gabe-mod, if I'm not mistaken.

But where is hidden the actual informations about this japanese sniper unit, like it's texture, it's .mdb file, etc. -> this is what I don't know! And actually, I'm not sure either if this information could be of any use to us.
*Historycally, there was stories of russian and german snipers inside the city of Stalingrad, for example... so from a RPG point of view...