Venice is so underpowered that everyone universally agrees that they are worthless in multiplayer, and I know everyone in my inner circle will roll a D100 instead of hitting Random Civ so that they do not get Venice in single player. As Venice is fundamentally unchanged in the CBP mod, I suggest strengthening them in some drastic way.
It feels *dangerous* to have Austria, India, America and a few others in any game, because those civs can do horrible things to you without ever going to war. America can buy your tiles. India can passively leach your faith by forcing you to buy defensive holy units. Austria can lock down a city state for *the entire game.* Venice needs to feel dangerous (which they sort of do, knowing that any city state can turn into one of their cities) without having an incredibly easy, near-exploitable way to shut them down. Single player? Conquer their capital asap. He's wonder-whoring anyway and won't have very many troops. Multiplayer? Immediately declare war and eat those sweet, nummy trade routes--you know where they'll eventually be.
What are some ways we can strengthen Venice without making them a fundamentally different civ?
What if Venetian merchants could buy any puppet or city with a courthouse?
Or, screw it, what if they can buy any city, ala America buying tiles?
What if they can additionally build great merchants in Venice while still being able to earn them?
What if Venetian cargo ships and caravans can escape plunder, or othewise defend themselves? What if Venice can always trade with enemies, and any trade route unit started after going to war has a promotion called "Merchant Treaties" making them unable to be plundered by a specific enemy?
First of all, I don't see the interaction between Venice and Austria at all, if anything Venice can totally kill Austrias UA by buying their married city-states, can't they?
Now back to the topic at hand. I'm going to analyze Venice out of a vanilla perspective, mostly because not much have actually changed for them.
In multiplayer, the civ is completely useless, because it is impossible to defend your cities with them being spread out, it is close to impossible to benefit from the extra traderoutes, because any other player you send the tradeunits to will just DoW you, killing your economy. Buying things in your puppets is completely useless, mostly because gold is extremely rare in multiplayer, because you can't run traderoutes. Honestly everything about Venice is just easily exploitable for other players, they can forward-settle on top of you and just rush you down because you only have 1 city's worth of production.
In single-player on the other hand Venice is one of the absolutely stronest civs in the game, higher difficulty city-states overspam units like crazy, so you can pretty much buy a city-state lategame, use their units to take two or 3 other cities easily. Double trade-routes is crazy, trade-routes is your main source of income, providing tons of gold while not increasing costs at all, unlike most other sources of income like building more cities is going to eat away at your income with extra maintenance.
Double trade routes also means double science from trade-routes, which is super-powerful on higher difficulties, trade-routes being one of the ways you can actually catch up on science. Sure, you're still going to have problems, but the AI is a lot worse at exploiting Venice inherent weaknesses.
I have no problem with doing some basic changes to Venice, but please don't try saying that the reason is because they are weak in single-player.