I like the idea. Epistolary novels can be quite good.
Have you read any Mikhail Ghishkin? One of the best contemporary novelists out there imo. His epistolary novel
Pismovnik (The Light and the Dark english translation) is excellent.
Some of my favourites in the style are Goethe's
Sorrows of Young Werther, Hölderlin's
Hyperion, and I always especially loved Montesquieu's
Lettre's Persanes. If you haven't read the last, I highly recommend you do.