> You can’t, for example, modify any of the template data fetching helpers.

how is this different from forking the engine? I'm not super familiar with Ghost's internals, but wouldn't this basically count as a fork anyway? Seems like you either have the option to change the internal engine code, or you don't. I think it makes sense that there aren't a lot of "in-between" options, because that's just asking for unannounced breakage when your "auto-update" system decides to overwrite whatever files you've already messed with, or change the files that are downstream from that one (breaking compatibility)