If you want to share some memory, "use" all required modules and start threading,

Unless the application requires all the modules in all the threads, that is bad advice. It ensures that every thread will get it own copy of everything in every module, whether it ever uses it or not. And if the application does require all of those in every thread, it is badly designed and probably won't work anyway.

If the OP structures his application properly, and requires only those modules he needs in each thread, it will reduce memory consumption conspicuously.

But you're right that the simplest route to reducing memory consumption is to avoid behemoth frameworks that force you to load everything before you can do the simplest thing, and a shit-load more every time you want to do something extra.