The first game was level 7, the new game is level 8. After cutting the road you will NOT get the lux anymore. However, if you trade for hard goods, such as lump sums or techs, you will keep those after cutting the road. Also, you can start the AIs warring against each other via military alliances, while you can duck out of those wars, since the military alliances get canceled via the cutting of the trade route. As long as you don't have any trade routes to your capital, it should work. So, if you have no harbors elsewhere, and no land routes to your "friend", selling a harbor in your capital should work. Though, does that really work out as the better way to go?
By 250 BC with some 8000+ already in the bank, at 70% luxuries, 30% taxes I've managed +1000 gpt in this one. Not sure if I like the map though, as it seems I might have two continents instead of a large pangea.