Sub-Domain Redirects to Money Site = DA Boost?

I have a PBN domain that I purchased that is an exact niche match to a client website (it was formerly a directory type site for this niche). The domain has pretty strong metrics, and I was intending on building it out as part of my PBN. However, my client's money site has pretty weak Domain Authority and I was thinking about just redirecting this domain to theirs for the boost. But it seemed a waste to redirect it to a single money site when I could us it for multiple sites as part of a PBN.

Then I got to thinking: What if I create a subdomain on this domain, and redirect THAT to the money site? That would push the DA to the money site without wasting the domain. I could then build the domain out as a PBN site as planned and just link to the subdomain in the footer.

Thoughts?

No one has any thoughts on this?

Also I would like to know more...