In the past I've used some online object simplify until it (the sites) has disappear.
I've needed to make the sh3d files less weight and more responsive.
There is already a tool HugeFileCleaner but not a tool to reduce the obj files size.
I think by reducing (optimizing) every object will make the project to be more easy to display on a html viewer.
As a separate application could be write even in C++ and made it cross platform and free.
In my view, this tool could have integrated an mechanism to identify all objects and their size (a table) along with the suggestion of which could be reduced without loos too much.
The user could have the option to optimize or not some of them (check).
After optimization the resulted file need to remain usable by SH3D.
One option could be to improve the Huge File Cleaner.
Anyway I'm on your side.