It's awkward, to say the least, for a passenger to get from one tramp to the other while someone is sitting in the cockpit. If your partner doesn't want to take over in the cockpit, another alternative is for her to remain on the starboard tramp and for you to control the boat from the port tramp, when on a port tack. (The rudder lever is on the port side). Obviously, you can't pedal from there, but this is a manoeuvre you only really need to carry out in a moderate to strong breeze.
It's not really necessary, but I have, in the past, set up an Ocean Kayak seat on the trampoline. This is a bit more comfortable for the passenger and gives them some extra straps to hold on to.
I wiil stick to a post I've placed here and on other forums numerous times:
Get an inflatable Stand Up Paddle Board. (SUP)!
It has the ability to simply slide on your akas to provide seating, be partly deflated as a large Air Mattress or in the extreme use as a means to stabilize a patient with serious injuries and float them to shore where a rescue chopper can tie them off to their skids for rapid transfer to an ER.
They also are a ton of fun to run gear and crew to the beach and back.
And last but certainly not the least as a lifeboat in case you crash and burn your AI/TI.