It depends how close your ‘re-creation’ is. If it is not distinguishable from a copy or conversion, then you are certainly open to trouble. Law is based on human judgement, not hard rules like coding. Note that being heigher resolution doesn’t save you. It is easy to scale textures up or further tesselate models. Even if you looked at an ET texture, and painted your new one by hand such that it looked like the original, it could still be a copy or a derived work in the eyes of the law.
That said, this sounds like a truely horrible waste of time. Remember, ET represents several person-years of work, and they had the advantage of having all the RTCW stuff available to them. While having layout and design work already done will save you some time, I would still be completely shocked if you did it in less than a year of full time work.
There are a lot of assets in ET. If you think you can create the equivelent of all ETs textures, sounds and models from scratch, with comperable detail, in less than a year of work, you either have no clue of the time required for this sort of thing, or you are a superman. That or your idea of ‘creating’ invovles ripping off the existing stuff and trying to disguise the fact. And that doesn’t even include the code, or re-creating the maps with some other toolset. You are talking about the same amount of work as a brand new total conversion, minus a little bit of game balance testing and map design.
And for what ? Something that is very much like ET already is, but on a different engine… If you really have that much skill, time and energy to put into creating a mod, I suggest you create something new. You could still use the basic class concepts, weapon balance ideas and so on, but you would end up with something new, and no threat of legal action.