Beware premature optimisation (making non-standard, over-complex design decisions based on untested performance assumptions)

You're looking at making the database bigger, removing any update/delete constraints for these lookups, adding extra code, unusual check constraints in a non-standard way of doing things that could lead to unanticipated errors when changing data in the child table, with no testing to see if the foreign key/join design it'll be replacing is inefficient.