I'd like this too.
The perfect general solution would be to allow identical, total control over the data type, behavior and display characteristics of all custom fields (and perhaps some "standard" fields).
While we're wishing, how about similar behavior/display control over view columns, so a column could display data differently in one view than another, and/or differently than in the properties field. For instance, a rating field might show a numeric value in one place, because it uses the least space and is easy to edit by typing (or even to compute from other values), but show a set of stars in another place -- all under user control.
Compute? Sure, assuming the "star" rating is actually stored as a number. Maybe the user assigns codes or scores to different aspects of a recording (as is done in music catalogs), and the user creates a formula to combine and weight these values to determine a summary score which is then displayed via a rating number and/or stars, and/or used to control smartlists.