You see, a mission board understands missionaries. Churches probably do to some degree, but it is not their specialty. ABWE specializes in training missionaries, taking care of missionaries, mobilizing missionaries, counseling missionaries and networking in missionary resources. When we had way too many bad boat rides and were ready to give up, our administrators told us we were not bad people for feeling that way. They told us they loved us and we were doing a good job. They told us to take breaks when we needed breaks. They loved us so much.
ABWE does not take the place of our home church, it aids our home church. The home church is the sender and the board is the facilitator. When one is sent out of a home church with no board, they do not have the networking resources. ABWE has a structure all set up to help with accountability and support on the field. They are also able to get international health insurance at a group rate. They have developed high quality internationally friendly evangelism and discipleship material. They understand how different cultures work and how to prepare for the life of a missionary.
Before we arrived on the field we were required to attend several training seminars. We were told what to expect. That understanding can save the life of a missionary who will face daunting cultural challenges.
So yes, be a great home church; and sure, support them for 100%. But make sure that you are connected to the resources you need to make your missionary as successful as he can be.