We even give up on the third room due to him expressing frustration with the other permits needed to inspect the septic and the extra time the project would have delay.

For this unit, I purchased from Lowes online, used my military discount, and set up the delivery right to the property.

Always remember there is no "tone of voice" or facial expression to read in posts, and perhaps give the poster a break. 

Everything on top is just a fancier way of expressing the same basic principles. 

Is your cousin picking finishes, keeping track of contractors and payment,  arranging deliveries etc?

Such as what you have expressed. 

The mail carrier has attempted delivery twice and now the mail piece is on its way back to me, "unclaimed."

A lot of people shipping items to Maui use DHX also, dependable Hawaiian Express. 

I'm interested in a remote-access system so that people can buzz in deliveries even if they're not home since we don't have a doorman (and packages get stolen all the time here if left on the steps).

Said disbursement instrux cannot be modified without the expressed written consent of both buyer and seller.