Once you are moving planets, many Earthlike planets can orbit the Sun. A wide variety of factors affect a planet's habitability, like atmosphere density, geological activity, albedo, stellar radiation received, rotation speed, water content, magnetic fields, moons, atmospheric composition, continent placement, and many other factors. I wouldn't be surprised if a conventionally habitable planet can fit round the Sun anywhere from Mercury's orbit to Saturn's orbit, just by adjusting the various parameters, perhaps to unlikely but possible values.
In fact, with Solsys being popular among modosophonts for being the birthplace of terragenkind, perhaps a transapient would do exactly that, e.g. create a Counter-Earth and Counter-Luna opposite Earth in the same orbit, to create the most faithful Earth replica possible. (Barring simulations of course)
For your original question, a 2-Earth-Mass planet opposite Venus in its orbit could easily be habitable. Low levels of CO2, oceans, atmosphere with many water vapor clouds, ecosystem designed to be light colours to reflect sunlight, continents at poles to create icecaps, etc.
In fact, with Solsys being popular among modosophonts for being the birthplace of terragenkind, perhaps a transapient would do exactly that, e.g. create a Counter-Earth and Counter-Luna opposite Earth in the same orbit, to create the most faithful Earth replica possible. (Barring simulations of course)
For your original question, a 2-Earth-Mass planet opposite Venus in its orbit could easily be habitable. Low levels of CO2, oceans, atmosphere with many water vapor clouds, ecosystem designed to be light colours to reflect sunlight, continents at poles to create icecaps, etc.