Facelookbovvered:
You miss my point completely. If Mr or Mrs Businessperson want to travel via AMS to, say Jakarta from EMA using BMI Baby, they have to check in at EMA to AMS, then on arrival clear immigration, get their hold baggage off the carousel, then go around to departures to checkin with KLM for the flight to Jakarta.
If they were able to fly with KLM from EMA, they would check-in at EMA, get boarding passes issued for EMA/AMS and AMS/JKT, and they bag would be checked through to JKT.
The time and hassle of the BMI Baby option is such that driving to BHX / MAN / LBA and flying KL is more viable, but still timewasting compared with a through routing on KL from EMA, were such a service to exist. CGN is neither daily, nor routing through a major hub airport (CGN is not a major hub airport for LH). BRU is indeed thrice daily, but it is probably the least useful of all the possible hub airports in continental Europe in terms of range of services offered.
Air Humberside
This suggests that it's not a case of BMI not wanting service FRA, but the parent not letting go of valuable long haul slots to make it possible. LH clearly still believe their hub in the Midlands is BHX. EMA's management needs to stop chasing LoCo and seriously go after KLM. Liverpool surely did, and it has resulted in a multi times daily connection to a major hub.