No original WWI plane could get a flying certificate, but thankfully there have been replicas for a while.
For planes its static originals or completely rebuilds which are almost a replica. Even if a like for like, proper copy, replica then no one would really mind.
I think there is strong argument for Museum pieces to be as original as possible and reflect the real vehicle warts and all, rather than a hash up of parts to make up something that never really was. Its all in the provenance and really should be complete as possible with some restoration which might include the bare necessities of new parts, or newly made parts. But added non original to the vehicle should be kept to the absolute minimum.
Anything other is a mash up of parts even if original parts. Nice but not correct, and interesting but the provenance is all but shrapnel.
After that its a reproduction that might have some original parts just because their available.
I think whats important is that replicas look right and sit and ride right. Sadly, so many just don't and there are some big failures. Like actors with too much plastic surgery, just look all wrong. A good or great replica should reflect at least on the outside what its trying to portray. Done badly they don't even do that.
A Copy is as close to the original that can be done. More than a replica. Though replicas can have a lot of copied parts.
Nothing wrong with a copy, or a replica, but each will have to be taken on raw merit.
Always a tricky one.