The new launcher runs a checksum comparison when it is started, to determine whether the current installation is up to date or not, or if it contains any corrupted files.
The problem that arises from this is, that it makes it impossible to install clientside mods, as the launcher will detect a checksum mismatch and thus not permit the modified game to be launched.
The previous launcher worked with checksums too, however it only compared them, when the user ordered the launcher to update, to determine whether or not an update was necessary, the it relied on the information in the version.txt
I request a way to at least manually excempt certain files from this check, or to disable the initial check, and only perform it when an update is necessary.