I would like to see Mozilla modularize Firefox more. Browsers are such huge beasts that contain everything imaginable plus the kitchen sink these days. It would be nice for these kinds of features to be add-ons that can be disabled or deleted if their functionality is not needed or desired, freeing resources for other use.

They can be part of the initial install so that Mozilla can provide the browser as they envision it, but be able to be removed for those who have other ideas of what their browser should consist of.

I don't know how technically feasible that is with their code, but it makes sense to me from a developer standpoint.