Actually, I think you have that 180 out, or maybe it's your use of the word 'could', which offers a choice. A restoration needs to be true to the original (as practically possible) while a replica is a 'look like'.I think the aviation requirements differ depending on whether it's a restoration or a replica. There's certainly been debates on how much original aircraft is required to be called a restoration as opposed to a replica.
If you restored a Sopwith Camel you could use a rotary engine. i doubt you'd be able to do that with a replica no matter how 'authentic' it is.