Sorry for ringing in late - just seeing this thread as we've been out in Yellowstone/ South Central Montana in our Hallmark enjoying the fall colors and fishing!
First, a well-optioned Hallmark and I'm sure you'll love it. After just spending a lot of time in mine, I can't think of anything I'd add to your list. You rig sounds very similar to ours actually. A few comments - my wife (5' 2") loves the booster step for getting into the cab-over - good addition! And the shower/porta-potty set-up has worked very well for us (I love avoiding dump stations).
Maybe the only thing I would have changed was fewer cigarette lighter plugs (we have 4) and more USB charging plugs, but we just use an adapter to charge phones so not a big issue.
Did you end up getting the ladder? I didn't think I'd ever use ours but its turned out to be very handy.
And something you are probably already aware of but you can spec about any material you want (in any color). We have sunbrella and it is wearing like iron.
Can't wait to see pictures of your finished unit. When is delivery?
-Vic