A file check option would be really great to have in the launcher. If a file is corrupt, let the launcher grab -just- that file instead of sometimes gigabyte-large patch files that have be applied in order. Even if SE just updated the base packages more often, that would be nice.

Or like, differential client updates and/or streaming updates like other games. This could be particularly useful for new players where they could begin the 2.0 story after the ARR bits are done being downloaded while the launcher grabs HW and SB.