In that case, I'd update my take on this pitch to be +1 if and only if it is accompanied by changes to build tools that allow marking code in a "separate SPM package within an Xcode workspace alongside a traditional Xcode project" as being within the same "package." Without that, my previous -1 comments apply.
(I realize that is essentially a completely separate team that probably cannot comment on whether or not that will happen for now, but worth stating anyways IMO.)