Re: Design/template/design editor in admin.
I thought it was possible now to edit the template and still upgrade without problems? Seems a bit weird that if you have designed your own design (template), you can't upgrade?
Yes you can upgrade, but you need to have used the template overrides so that your design is not wiped out by the upgrade and then you would upgrade your templates if there were changes to the code in them.
Your idea could work, but is somewhat flawed as it doesn't take into account many of the features already available - such as being able to turn the banners on and off from the Admin and being able to disable the side columns, both of which are built-in now.
While being able to choose colors from the admin would be nice, you are limiting the possibilities of being able to use images for the backgrounds in all the various elements. Your approach seems like it would not have the ability to have more than one template available for use, example a seasonal template or a template based on the language.
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