With the abundance of custom Dash Fabrications available today, you could possibly find one who could fab a large format rectangular one for you...that is, if you could afford the tab. Most likely a swivel-eye mounting that you infer, might not exist, as it assumes that a dash mounting location would need to have two persons view it from opposite directions of 130 degrees. [that being the case, a standard flat-mounted display would be the default format since it's assumed both pilot & copilot are seated within close proximity of each other.] A much wider RV cabin seating viewpoint would be an extreme unique situation to deal with & not in the mainstream of marketability.
I personally prefer my co-pilot to watch the GPS. [as mentioned above...I would buy a stand-alone GPS just for her to monitor. I just don't think it safe for me to fiddle with setting, query or doing any serious use with the unit while my attention needs to be 100% on "Driving" & watching my surrounding traffic friends.
FWIW, even your "swivel-mounting" would not place the GPS any closer to her for any manual use-of-functions without her removing her seat belt.[unless she's possibly Left-handed and can reach it with outstretched hand. My DW has to have it within eighteen inches of her eyes for her to "operate" the functions. Any further a distance from her is useless to ask her to operate. She has to have it far closer to her.