Allocating new members to new members in a single dimension (Design question)

Hello,

We have a requirement for one of the allocations where end users will create a new Project. This new project will have to allocate to other new project members.

A design option (I am trying to avoid), is to use a duplicate project dimension. The rule would use "Source Project" as source pool of dollars, where the driver would have the allocation percentage on the target projects.

This allows users to create a "new" allocation on the fly.

But obviously duplicating a project dimension would be wholly inefficient (especially as we are talking potentially 40k plus members in both dimensions).