bmi regional also operates BRS-FRA up to 3 x daily and BRS-MUC up to 2 x daily as LH code shares and, as you say, the sector fares to/from FRA and MUC for someone just flying point to point can be expensive.
When bmir obtained the code shares the passenger figures on the BRS routes improved noticeably, so a similar thing for DSA would be extremely helpful.