Sorry for the delay in replying!
This is possible; it isn't super duper easy right now, though. What you'll have to do is manually set up a transfer function using ColorTransferFunction. This has the option to set multiple fields, and multiple alphas; you'll then tie field interpolation tables to different fields, along with alpha.
It's not ... super duper easy right now. If you look at how the PlanckTransferFunction is set up, you can see how this is used to have temperature specify the color and density the emissivity and alpha.
I wish I had a better answer!