Taking assets from one game and placing them into another is obviously copyright infringement, and is therefore something the modding community either frowns on if not actually bans due to legal ramifications.
So directly turning an old game into a newer game, and vice versa, all from within internal assets is just plain bad for the gaming industry and community as this can damage sales due to being able to recycle content rendering new game purchases pretty much irrelevant...
...but indirectly turning an old game into a newer game, and vice versa, all from external assets (personal modders' creations) is just plain good for the industry and community as (Dick said earlier) we could all pull together and fix or just improve on the developers work, resulting in increased popularity and therefore sales.
However, I'll say though that if a developer has a franchise with annual releases that basically contains the same core system / engine every year, and only have a few chronological variables adjusted between releases, then they're obviously leaving the door wide open to the situation / issue in question. If they change things so significantly, i.e. from 2014 to 2015 and the community can't mod the newer game, then they're obviously entitled to do this, so in a way it doesn't really matter what we think, but if they're going to block us out then they better make damn sure they get the game right, or risk losing the entire F1 franchise rights.
As for the question of "if mods based on transferable content / assets should be allowed or banned on websites such as Race Department" - well, RD can chose to do whatever it wants to do, and I'm obviously not speaking on behalf of them, but if what you say of them removing content that has been made while infringing copyright rules is true, then I'd say that they're doing the right thing in accordance with the law, and respecting Codemasters' property.