It can also be interesting to request an instrumentation that they don’t play very often - solo guitar, cello sonata, woodwind quintet, accordion, organ, etc.
Nationality can work - Argentine, Brazilian, Cuban, Canadian, Danish, etc.
If it’s a not-for-profit station, you might suggest that a prize for a silent auction or phone in could be to plan the playlist for a certain time-slot for one day.
CBC used to have a couple of interesting shows on the FM network - Gilmour’s Albums was a Vancouver music critic (Clyde Gilmour) who had a massive collection of albums, and once a week would take the country on a tour through his vinyl. There was also RSVP, which was a daily mail-in request show. Both long gone, alas…
It’s hard to program classical radio, which is why lots of stations fall into the trap of sticking to what is well established as ‘unoffensive’. Regular listeners want their horizons expanded, while infrequent listeners want the comfort of hearing something predictable. The trick is keeping both groups happy.
Villa-Lobos, Bernstein, Chopin, Regondi, Debussy, Francesco da Milano, there’s more beautiful music in this world than any of us have time to listen to, and that’s only in the classical section.
Good luck with it.