Going back a step, the number of extensions really depends on the quality of your data layer. If you are just developing your data layer like it sounds, I would suggest you build it as robust as possible. Even if you don't think you'll need the value now I would suggest thinking about future needs. What data points are you going to want in the future? This will significantly cut down on the number of extensions.
However, using extensions is inevitable, but that is the benefit of working with Tealium :) So I would recommend using the Labels feature in the UI. This will allow you to filter the extensions on the labels you have created. That way you don't have to sift through all the extensions.