Exponent v. Proponent in Cochems
Either word is correct.
Exponent, I think, is better,
1. a person or thing that expounds, explains, or interprets: an exponent of modern theory in the arts.
2. a person or thing that is a representative, advocate, type, or symbol of something: Lincoln is an exponent of American democracy.
An exponent is more than a proponent. Cochems by his writings was an exponent.