My idea of ideal location may be different from yours, but we loved this 2-bedroom apartment in Trasverere, on Piazza San Giovanni Della Malva, just steps from Ponte Sisto. We like to walk, and could walk to the Vatican in 30 minutes, or to the Forum area in a little more. Or we could take the tram line that runs from Trastevere to the historic center at Torre Argentina. Piazza Navona area was a bit further, but still walkable. We did use a taxi to return from Villa Borghese after walking there.
The apartment is very modern and nicely furnished—-the photos are accurate. The rooftop terrace has 2 levels. The kitchen is tiny, with little eating space, but we enjoy dining on the terrace anyway. There are a lot of steps, and the kitchen, the master bedroom/living area, and second bedroom are all on different levels. That might be a negative for some people, but we did not mind.
One problem with sharing it with another couple is the difference in size between the master suite and the second bedroom, and the bathrooms attached to each. Also, the access to the rooftop terrace goes through the second bedroom. But maybe with a long stay you could switch bedrooms halfway through, so you could each experience the benefits and the downside of each room.
We rented it on TripAdvisor, so I will post that link. It is also on Air BnB, but with a different host—-not sure what that means. Perhaps Lorenzo (who is a gracious host and lives in the adjacent apartment) got married after we were there in 2015, or maybe he listed the Malva Palace with an agent. It may be on VRBO as well.
https://www.tripadvisor.com/VacationRentalReview-g187791-d4578715-or6-Malva_Palace-Rome_Lazio.html
