The CA (and AZ) model could be improved by a better set of criteria. Many of the criteria are left as "touchy-feely" items that the commission can define on the fly. If commissioners have strong opinions, particularly on non-political criteria, they can sway votes to reflect their bias. One area of tension in commission criteria is in the use of political data. If one wants competitive districts one must use that data, yet that data can be manipulated to create a partisan bias (see AZ). I don't mind a commission system, as long as they have objective criteria that are defined before they start mapping.
I wouldn't compare the California system with that of Arizona. I don't recall California using political data when drawing the current lines. I do believe those that draw the lines in California are forbidden from using political data.
I wouldn't support a legislature vetoing a map wholesale like Iowa. If we're going to allow alterations to the map, perhaps we could have something like Washington (which I believe allows for minimal changes to the commission's map).
