Your example works because English pronouns are the only nouns in English which still have different forms for parts of speech (e.g., nominative I, possessive my, objective me; he, his, him; they, their, them). In other languages all nouns have different forms for different parts of speech.
In languages like Latin, adjectives also have different forms which match the nouns they modify, making word order flexible without being ambiguous. In English, adjectives usually must preceed the nouns they are attached to, save a few exceptions (attorneys general, tacos supreme, Optimus Prime).
You've gotten a benefit from having an indirect object expressed with a preposition, but presumably a lot of verbs don't take an indirect object and don't have a synonym that can.
In that case, it's probably not best analyzed as an adjective, unless we want to analyze "Senator" as an adjective in "Senator Wyden" or "Mister" as an adjective in "Mister Rogers".
In languages like Latin, adjectives also have different forms which match the nouns they modify, making word order flexible without being ambiguous. In English, adjectives usually must preceed the nouns they are attached to, save a few exceptions (attorneys general, tacos supreme, Optimus Prime).