I'd say hacks (what some call mods) rather destroyed old IL2 (remember, what you call mods in old IL2 is based on leaked hacked code) than really added things. A few planes more? Some additional maps? Great! Most of it was there before the hack.

Now we have infinite number of old IL2 versions making it very difficult to fly together online.

I know how old IL2 was before hacks and the content was there well before the hacks (people seem to forget that the huge amount of planes available in old IL2 came with patches from the dev team without any addition from modders. Same with the maps). IL2 was huge well before the hack. So "Ehre, wem Ehre gebührt" (Honour to those who earned it).

To the initial concern on skin using:
I use some custom made skins offline and had no problems up to now.