Tooling I can believe. Dies don't care where they'll be used. But equipment? No. You have to know where that stuff is going and how it will interface with pre-existing building and equipment (if any).
They originally spec'd Model 3 stamping, body and paint for 10k/week. That's a very normal 2 shift factory. They ran into some problems and assembly turned into a disaster, so they re-targeted for 7k/week. The new level was roughly based on 3k for each internal final assembly line plus 1k in the tent.
The obvious "capex-light" approach is to finally utilize the full 10k capacity for stamping, body and paint and add third 3k/week internal final assembly line (GA5) for Model Y. They can also assemble Y in the tent and re-fit one or both of the two existing internal GA lines so they can switch between 3 and Y.
With this approach 3+Y target volume is 10k/week. I figure the split will be 60-70% Y after a year or so.