Thanks for the reply!
After a talking to a couple of other sparkies I know, I mostly went this way:
1) 2x primary metering. One for rental (100A). One for shop (300A). House is a sub off the main shop panel.
The 300A is now up to a full 400A to maximize the equipment. Separate triplex run in for the rental. I made sure there was a generous distance between the 400A splitter and the 200A switch (for the house) to accomodate a transfer switch and at a later date.