The a/c is based in MSP as is the company, mechanics and flight attendants. There is a laundry list of about a thousand checks and people to train on the actual a/c before it goes into service. That requires it to be in MSP. If it is required to be in MSP it cannot possibly go to every out station to allow its agents to practice at any length on the docking procedures of the jet bridge. Yes, Mesaba has actually thought about the training aspect for this, but as said before, these are teething issues that arise with a new a/c type.
AZJ