Will content-blocks be treated like content-elements, in the way that we can adjust the permissions of which BE user/usergroup can see/use which block? If so, than I’d prefer the bundling of blocks in one package.
The reason is, that as agency we’ve created an extension/package of custom elements/blocks anyway, which can be used in multiple projects (e.g. can be seen as a “agency base template extension with common features and CE’s where each customer extension is build on top of”). Through editor permissions the needed elements/blocks will be activated for each project.
Like the other feedback above, I don’t see a reason why each block should be available as stand-alone package: 1) common used blocks could be bundled in an own extension described above, and 2) they might be too specific to share across projects anyway.
The base TYPO3 installation could ship with a bundle of standard blocks, like with the standard elements right now.
Edit: After re-read the above, I support the point of Jonas Eberle “reuse blocks within your organisation” and the meta-package idea. Personally I just don’t want to see millions of single block-packages wasting packagist or the TER (see point related to slider extensions above).