I understand what you are saying. I agree that Plus has lots of features. And ironically its this that is stopping there from being a modular version.
Its easy to say that its possible to just have modules to select on install, but try to actually visualise the end product. How would the preferences panel actually look? Surely its going to be a lot of extra work for Patchou to make the panel dynamically built depending on what features were chosen. The prefences panel is already split up into modules. It doesn't seem to make sense to say remove one of them.
I understand you have concerns about memory usage having lots of extra features. Patchou has said that Plus uses around 1Mb of memory whereas Messenger itself can use around 15Mb, so it shouldn't really be an issue. That said, Plus 3.50 is supposed to use even less resources. So its all good