> Consider this, if the mod interface was C/C++, do you think those poorly optimized mods could be trusted to also not leak memory?

Garbage collection does not solve memory leak problems. For example

- keeping a reference too long,

- much more subtle: having a reference to some object inside some closure

will also cause memory leaks in a garbage-collected language.

The proper solution is to consider what you name "poorly optimized mods" to be highly experimental (only those who are of very high quality can be treated differently).