How do the in-game options of No Tech Trading and No Tech Brokering work?
Do they affect AIs and players alike?
Can you still always trade Gold or is there a way to shut off the ability to trade lump sums of Gold?
An alternative approach is to simply allow tech trading. One reason for disallowing it was to avoid Fair and Forthright Trading bonuses, but you could still get those with Resource gifts, just not as quickly. I'm not sure that Diplo or AP would actually become any easier... sure, you can bribe AIs with gifts, but other players could equally "Trade with a Worst Enemy," thus cancelling out the +4 Fair and Forthright Trading bonus with a -4 You Traded with our Worst Enemy penalty. With tech trading on, though, I'd say push the game up to Deity level.
Did we have any other reasons for avoiding tech trading besides the +4 Fair and Forthright trading boost? Certainly it makes a Space game extremely difficult. I suppose that there is always the "bribe one AI into war against another strategically" option, but how often does that option come up on Deity level? Not enough for it to be game-breaking.
It probably wouldn't hurt to make it a Continents game... that way, an early Conquest can't clean house and the team has a relatively common goal of at least making it to Astronomy. It was fun having somewhat common goals at the start and if we prolonged that period for a bit, I think that it would make for a better game at Deity level... it's hard to start sabotaging each other from the second turnset onwards if we're playing on Deity.
The game could potentially be played as the French, so that the Salon Unique Building (free Artist Specialist with an Observatory) will make it a bit easier for the Cultural Victory player to spawn Great Artists, which would go hand-in-hand with Astronomy (most other players would build this Building on behalf of the Cultural Victory player).
That said, I think that having a Spiritual Leader is a key part of the game, to avoid Civic swaps getting in the way of each competing player.
If we were to play with Unrestricted Leaders, then we could pick the French and a Spiritual Leader. Another alternative would be the Chinese, since their Unique Building adds a good bonus to Culture and their Unique Unit would be fun to help in conquesting the original continent. The Ethiopians, while they have a Culture-enhancing Unique Building, would not be a good choice, since their Unique Building's unique power obsoletes with Astronomy. Basically, I think that we can all admit that a Cultural Victory is probably the hardest to win with, so it doesn't hurt to play with a Civ that slightly favours a Cultural Victory player.