A little late, but I figure I'll chime in. If you don't weld (like me), if you can dream of ever doing it, make sure you build it into your system the first time. It is always more expensive to add it later. I am on my second brew stand and have had each modified to adapt with my brewing desires. Both times, they were things I said I would never need. Do it once and save the money.
I would suggest going single tier since you are already using a pump. One problem with having the boil kettle lower is you will have to get your pump that much lower so that it can prime off the boil kettle. Because when your kettle is lower, you can't gravity drain into the fermenter. You'll need a pump at nearly every other point. So it makes sense to have everything at one height.
A work shelf is a great addition. I don't have one on this stand and wish I did. You can make it fold down to save space.
Have some uprights so that it is easier to do water plumbing to your kettles.
Make sure you get a cover made for your pump.
Pegs to hold spoons are nice.
Casters. Have them before he starts so he can do the holes in the feet for them.
Go big and go deep. I'm glad I did major overkill on the size of the tubing I used. I'm glad I built it big enough to accommodate another could of kettle sizes up. I'm also glad that I made it deep enough so that it doesn't feel like it's going to tip over.
Make sure you have a place to mount the arm for a control panel. Have a plate built so that you can mount a switch for a pump if you aren't doing a control panel.
Maybe an extra pump mounting point in case you ever go to two pumps.
Place to mount a water filter.