This will not work, as it is not the extension itself (nor the RBZ archive) that does the installing. It is either SketchUp itself (via the “Install Extension…” button,) or the EW website, or a 3rd party website like SketchUcation’s PluginStore extension.
“it” here is the SketchUp internal startup code, which is hard-coded in all versions. Old versions will not be getting patched to change behavior.
But, in fact, the startup load behavior has changed over the versions. All old versions with Ruby 1.8 loaded the “Tools” folder last, began loading the program child “Plugins” folder first, and branched off to load other folders elsewhere depending upon
require_all calls in loading code, or via the presence of some 3rd party utility (like the one example I have posted at SCF, or the Additional Folders extension. There may be others.)
Sometime after SketchUp switched to Ruby 2.0 (SU2014) the “Tools” folder is now loaded first, along with rubygems and a bunch of encoding libraries.
Then the user “Plugins” and the public “Plugins” folders are processed (not sure in which order.)
I suppose an extension could be written to add a sub-folder loader loop to old SketchUp versions. But this will bring up a common occurrence we have now.
Users do not read install instructions. Even now when a library is required for an extension, they don’t read the requirements, and install the extensions without the library and then post “HELP!” threads in the forum with out searching for answers first. The extension authors (and other gurus) waste a bunch of time answering these posts.
So we would have users installing the new format extensions in old SketchUp versions, without also installing the “load loop” extension.
Lastly, there would need to be a easy way to know the difference between the package formats. A new archive file extension like
.skez (SketchUp Extension Ziparchive)