RE:RE:Question for SheDrillsmrbb, geomanx02, They'd do a multizone completion (see link below). My friend is involved with them. I know little about them. They require a rig with a big moon pool to get the subsea trees through, custom designed surface equipment to test the trees and move them over to the moon pool area.
The multizone completions strings can be designed in a variety of manners as per link below which also says that you don't want to commingle different fluid types with different drivers (water, gas injection) so I guess knowing what the formation fluid type and what you drive it are critical completions design criteria.
There are case studies on the internet that you can read up on done in the GOM. The completions are preceded by months of analysis, design before they go into the manufacturing stage of the equipment because it appears that for HTHP deep water eveything is custom manufactured and nothing is off of the shelf. So yes, mrbb tens of millions of dollars just to complete the play and that doesn't include FPSO and injection wells.
I remember reading that Exxon has one rig dedicated just for doing completions. So, my guess is that any possible JV partner is a company that has the experience, infrastructure and equipment already in place to pull off a deepwater completion or plans to have it soon or has lots of money and experience like a Chevron.
https://www.drillingmanual.com/multiple-zone-completion/