I hear you on that! I am ordained with the Progressive Christian Alliance and am trying to set up a post-mainline, progressive/emergent campus ministry at a local university. As far as I can see what I am trying to do/explore is:
1) Tradition - mainline churches are steeped in tradition. These are a great and beautiful poetry of faith and expression of faith. At their best they are life giving, at their worst they get so bogged down by rules they no longer work.
2) The death of the Mainline Denomination should not be the death of the Liberal Progressive Theological Tradition. Mainliners have fouht for decades for the full inclusion of women, LGBT folks as well as non-literal and freeing readings of the bible. That should not be lost.
3) entrepreneurial - Mainline churches have become so stuck in our hiearchies - our rules of who and is not in the church, who is and is not a priest etc - and this is true for 'bishop' systems and prebetery systems - that ground level, pew up innovation and creativity has become stiffled.
4) Music - a booming organ and 200 voices singing worked when you had 400 people in the church. Emerging Churches are moving away from contemporary music to traditional music. But I think mainliners - or post-mainliners - need to move towards contemporary music. Not the praise band - but finding new, innovative and creative ways to engage the cultrually-located worship language of it's people. I would love to see new hymns/songs that emerge from the people.
5) Hiearchies - have got to go. Many of them are based in ancient european politcal systems. I am a north american - I want congregational, democratic level leadership. How do we do this AND INCLUDE the wider tradition - how do we reframe the role of the bishop etc?
6) Denominations are dead! The future is made of networks or confederations of congregations of diverse worship and theological practices. Nodes in a network, instead of bricks in a pyramid.
7) Theology - how do we close the pew/pulpit gap and bring theology back to the people? How do we make it a liturgical work?