I know the current DNN version is only designed to work with MS SQL, but I think it would be great to have a choice to use MySql.  Is there any easy way to do this?  Maybe using LINQ?

I thought there may be some way to abstract the access to the db.  In other words some abstraction layer that should be written into future versions of DNN that would allow all of the modules and core to call a DNN API.  Then the Data providers could be written against that abstraction layer. Obviously this is a big architectural change that would need to be done to the application but seems like a good idea for a "framework". 

It still sounds like it is not abstracted enough.  Just imagine how Windows abstracts the Win32 API from the hardware.  The Win 32 api stays the same whether you have an Nvidia or ATI, Western Digital or Seagate, etc.  You call higher level functions and the rewiring is done down below.  This is what I am talking about for DNN.  There would be a higher level API and it would be a checkbox to select which data base you want.  This is not that important for me but not everyone wants MS SQL or MS SQL Xpress.  In my opinion rewriting every module to a new provider is not acceptable and just means that the modules should be abstracted more from the database.