In this "How To" thread it states that calling your plugins from an external script will cut down on memory usage.
https://vborg.vbsupport.ru/showthread.php?t=104657
I haven't upgraded to 3.5 yet, but plan to soon. Since there's a "how to" thread, I assume that this isn't the normal way plugins are installed. Since we plan to add a considerable amount of plugins and other mods, it would be nice if there was a mod that could automatically install them in an external script directory and add the appropriate php include code.