3 suggestions:

1. Blueprints could be cleaned in some way so that you get back an unwritten blueprint.
2. Different Texture for written blueprint (like a white scramble on it)
3. Pointing at a block with a blueprint in hand makes a semi-transparent version of the block appear, a "bit" like when using schematica mod.

i've made a simple datapack to add suggestion n.1.
Download Link
To have a clean blueprint simply put a written blueprint in crafting pattern and you get a clean one.