Reinventing the Political Platform

How to unite the vastly diverse Democratic Party?  That question, in the face of the Mighty Wurlitzer of the right-wing, arises again and again.  Perhaps the answer lies in the process rather than the policy.  After all, no matter where the line is drawn on policy, with all our diversity, many voters on both sides of the line will be marginalized.  

The discussion seems to always focus on drawing the line on policy so as to cast the widest net.  But can a wider net be woven with ideology rather than a hodgepodge of positions on issues?  Shouldn't policy reflect a more abstract ideology anyhow?  You might say that liberalism/conservatism is the ideology, but the definition, or rather the perception of these terms seems both unclear and a moving target.

So here's a process-based approach to unite the Democratic Party:  
Establish a layered political platform whereby the highest layer, the ideological layer, is generic enough to encompass or represent a wide array of constituents, but specific enough to define the Democratic Party uniquely.  The ideological layer of the platform should not change with each election, but should serve as a longer-term guide, more accessible to the average voter, and require some sort of democratic process to alter or amend.  The policy layer, or the position on specific issues, would then reflect the current political, economic and cultural environment and would therefore be re-established each election cycle, adhering to the traditional process of creating a political platform.

This approach is analogous to establishing a roadmap, or a vision, so that the discussion may then focus on how best to get there.  The question is, would people be more likely to vote based-on clearly defined ideology even if they don't agree with specific policies?  

Then again, I am a rookie in the world of politics, so while this approach seems pragmatic to me it may very well be naive.  If it is naive, how else to unite our Party?