The whole thing makes sense to me and I can't see any major points of criticism in the design rationale. Some thoughts:
* There is already a "native" Sqlite3 container solution called Sqlar [0].
* Sqlite3 itself is certainly suitable as a base and I wouldn't worry about its future at all.
* Pascal is also an interesting choice, it is not the hippest language nor a new kid on the block, but offers its own advantages as being "boring" and "normal". I am thinking especially of the Lindy effect [1].
All in all a nice surprise and I am curious to see the future of Pack. After all, it can only succeed if it gets a stable, critical mass of supporters, both from the user and maintainer spectrum.