I like Maruszczyk basses (I have 2 Elwoods and have owned a Jake), but the lower horn and scratchplate aways look overly bulbous to me, if they sharpened those contours up, just a touch, it'd be a winner.
Replicate this position with a strap, if possible. I certainly try to get my sitting and on the strap position as close as possible to each other. Conversely, play sitting down all the time perhaps?
Pretty much all you really need. I saw them on the Hysteria tour, it was just ok (Brian May came on at the end and they played Tie Your Mother Down), 40 or so years on, I imagine they would be slicker than oil on silk.