They'll never make alternate Infantry skins, because the skins are important in identifying a unit. This isn't a problem with vehicles because those are large and have distinct shapes. Infantry are small and roughly the same shape, so their skins are one way to quickly tell them apart.
Again this has to do with unit identification. Soviets are bright yellow-tan to make identification easy. Same with Americans who instead of olive green are fairly light green, which stands out and is unique, or Volksgrenadiers who have bright grey uniforms.
Absolutely irrelevant. Infantry units have never been and will never be identified primarily via the appearance and skins of their models. That's what the colored icons above them are for. Do you zoom in to tell Conscripts apart from Combat Engineers? No, you look at the colored icon above their head. If someone changes the camo, the cloths or whatever on them so they look more realistic, it has absolutely zero impact on the gameplay (unless they color units in neon pink or something maybe, but even that wouldn't really change the fact that the unit icon is the one ppl look at).