Does EllisLab ever choose to incorporate as standard any user submitted plugins and extensions that address shortcomings in EE as opposed to adding functionality?
The latter I can understand as it keeps EE lean and mean!
To date we have not included any third-party add-ons with the base application download, no. We do not have an official policy to that effect, but typically if something has enough of a broad need so as to be appropriate for including in the download by default, it’s best handled as a first-party feature. That way there is no question as to code ownership, quality, security, or who provides support.
Most of the time, though, third-party add-ons cover a specific need, and even if they are popular and cover the need well, we’d rather encourage their independent distribution and support of the add-on than always assimilate their hard work. Some companies have in fact built successful businesses around this, and that’s an area of the ExpressionEngine cottage industry that we’d like to encourage to grow.