how long would it take to burn through 255 addresses at only 3 TPS,
I think you haven't caught the real reason that 256 bit addresses are important. Any N-bit address has only N/2 bits of security against collision, right?
So here is the interesting attack: You give me your pubkey, and then I create my pubkey for a 2-of-2 (or some other more elaborate contract), and then we pay to the resulting address.
Oops. In the background I did ~2^80 work and found a colliding address which didn't have the same policy, and I use it to steal the funds.
2^80 is a lot of work, but it isn't enough to be considered secure by current standards.
Unrelated, it's also the case that many hashes of the same vintage of ripemd160 have been significantly broken or substantially weakened.
there's a lot of other "wasting room" on the transaction, and the most important one to me is the hash of 256 bits indicating the transaction. This is overkill. There is also the 32-bit number indicating the "output number of the transaction" as if transactions would contain 4 billion outputs. This is wasted space.
You are free to store transactions however you like and negoiate with your peers to send them however you like, there is no need for space to be wasted as a product of serialization. Using a larger hash does take up more resources but the difference is pretty small compared to the rest of the transaction.