Thank you for such detailed feedback! However, this post is intended to be a place where people can experiment with the feature. The syntax and the direction of this feature were discussed in a [Pitch] Enable pack iteration post.
As per what this proposal suggests, we are aiming to allow Swift users to iterate over packs and explicitly bind an element to a local variable. As @hborla mentioned, one of the important purposes of this proposal (and something that your syntax doesn't support) is to allow pattern matching with an element of the expansion. Also, the proposed syntax follows the progressive disclosure paradigm, where we let users use the familiar for-each syntax for pack iteration. Since you mention that your syntax can be equivalent to the normal for-each with a Sequence, it is debatable to add a new syntax for essentially the same logic as the existing for loop conveys.
Since the feature you are proposing seems to be orthogonal to this proposal, I would encourage you to move this discussion to a separate thread where you can explicitly propose the changes you'd like to make 